[infrastructure] Add unified admin CLI for self-hosted helpers (#6507)

## Summary

Adds a unified `admin` CLI for self-hosted instance administrators in
both the management and combined binaries.

## User Management

### `admin user change-password`
- Changes a local embedded IdP user's password.
- Selects the user with `--email` or `--user-id`.
- Reads the new password from `--password` or `--password-file`.
- Clears the user's local authentication session so the new password is
required on the next login.
- **Alias:** `admin user set-password`.

### `admin user reset-mfa`
- Resets a local embedded IdP user's MFA enrollment.
- Selects the user with `--email` or `--user-id`.
- Clears TOTP/WebAuthn enrollment data and removes the local
authentication session.
- The user will re-enroll MFA on the next login.

## MFA Management

### `admin mfa status`
- Shows whether local MFA is enabled in the account settings.
- Checks the embedded IdP client configuration and reports whether MFA
is enabled there.

### `admin mfa enable`
- Enables local MFA for embedded IdP users.
- Updates embedded IdP clients and saves the account MFA setting.
- Records an audit event on a best-effort basis.

### `admin mfa disable`
- Disables local MFA for embedded IdP users.
- Updates embedded IdP clients and saves the account MFA setting.
- Records an audit event on a best-effort basis.

## Reverse Proxy Tokens

### `admin token create --name <name> [--expires-in <duration>]`
- Creates a reverse proxy access token.
- Prints the plaintext token once, along with the token ID.
- `--expires-in` supports values such as `24h`, `30d`, or `365d`. If
omitted, the token never expires.

### `admin token list`
- Lists reverse proxy access tokens.
- Shows the token ID, name, creation date, expiration, last-used time,
and revocation status.
- **Alias:** `admin token ls`.

### `admin token revoke <token-id>`
- Revokes a reverse proxy access token.
- Revoked tokens can no longer authenticate reverse proxy instances.

## Reverse Proxy Management

### `admin proxy disconnect-all`
- Lists registered reverse proxy instances and force-marks all connected
instances as disconnected.
- Useful for repairing stale proxy state after an unclean management
server shutdown.
- Prompts for confirmation by default.
- `--dry-run` previews the changes without applying them.
- `--force` skips the confirmation prompt.
- Live proxies may appear again after their next heartbeat, reconnect,
or re-registration.

## Compatibility Commands

### `token ...`
- Deprecated top-level compatibility path.
- Behaves the same as `admin token ...`.
- Retained so existing scripts using `token create`, `token list`, or
`token revoke` continue to work.

## Changes

- Adds reusable `management/cmd/admin` command package.
- Wires `admin` into `netbird-mgmt` and `combined`.
- Adds local user password reset with existing password strength
validation.
- Adds local MFA enrollment reset by clearing Dex TOTP/WebAuthn
credentials and local auth sessions.
- Adds local MFA enable/disable/status helpers for embedded IdP
deployments.
- Moves proxy access token commands under `admin token` for a single
admin-focused CLI entry point.
- Exports `server.ValidatePassword` for reuse by CLI helpers.

## Tests

```bash
go test ./management/cmd/...
go test ./management/cmd/admin ./management/cmd ./combined/cmd
go test ./management/server -run TestValidatePassword
```

Pre-push lint also passed.


### Checklist
- [ ] Is it a bug fix
- [ ] Is a typo/documentation fix
- [x] Is a feature enhancement
- [ ] It is a refactor
- [ ] Created tests that fail without the change (if possible)
- [ ] This change does **not** modify the public API, gRPC protocols,
functionality behavior, CLI / service flags, or introduce a new feature
— **OR** I have discussed it with the NetBird team beforehand (link the
issue / Slack thread in the description). See
[CONTRIBUTING.md](https://github.com/netbirdio/netbird/blob/main/CONTRIBUTING.md#discuss-changes-with-the-netbird-team-first).

> By submitting this pull request, you confirm that you have read and
agree to the terms of the [Contributor License
Agreement](https://github.com/netbirdio/netbird/blob/main/CONTRIBUTOR_LICENSE_AGREEMENT.md).

## Documentation
Select exactly one:

- [x] I added/updated documentation for this change
- [ ] Documentation is **not needed** for this change (explain why)

### Docs PR URL (required if "docs added" is checked)
Paste the PR link from https://github.com/netbirdio/docs here:

https://github.com/netbirdio/docs/pull/832

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

## Release Notes

* **New Features**
* Added self-hosted admin CLI commands for changing passwords, resetting
MFA (including WebAuthn), and managing embedded IdP client MFA
(enable/disable/status).
* Introduced a unified admin command entry point and improved
data-directory handling for embedded IdP storage.

* **Refactor**
* Centralized password strength validation into a shared exported
validator.

* **Tests**
* Added a comprehensive admin command test suite covering password
input, selectors, MFA reset, and client MFA state handling.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

idp/dex/provider.go

@@ -40,7 +40,7 @@ type Config struct {
 	GRPCAddr string
 }
 
-const localConnectorID = "local"
+const LocalConnectorID = "local"
 
 // Provider wraps a Dex server
 type Provider struct {
@@ -494,18 +494,60 @@ func (p *Provider) Storage() storage.Storage {
 	return p.storage
 }
 
+// SetClientsMFAChain updates the MFAChain field on OAuth2 clients in Dex storage.
+// Pass a non-empty slice (e.g. []string{"default-totp"}) to enable MFA, or nil to disable it.
+func SetClientsMFAChain(ctx context.Context, st storage.Storage, clientIDs []string, mfaChain []string) error {
+	previousChains := make(map[string][]string, len(clientIDs))
+	for _, clientID := range clientIDs {
+		client, err := st.GetClient(ctx, clientID)
+		if err != nil {
+			return fmt.Errorf("failed to get client %s before MFA chain update: %w", clientID, err)
+		}
+		previousChains[clientID] = cloneMFAChain(client.MFAChain)
+	}
+
+	updatedClientIDs := make([]string, 0, len(clientIDs))
+	for _, clientID := range clientIDs {
+		if err := st.UpdateClient(ctx, clientID, func(old storage.Client) (storage.Client, error) {
+			old.MFAChain = cloneMFAChain(mfaChain)
+			return old, nil
+		}); err != nil {
+			if rollbackErr := rollbackClientsMFAChain(ctx, st, updatedClientIDs, previousChains); rollbackErr != nil {
+				return fmt.Errorf("failed to update MFA chain on client %s: %w (also failed to roll back previous MFA chains: %v)", clientID, err, rollbackErr)
+			}
+			return fmt.Errorf("failed to update MFA chain on client %s: %w", clientID, err)
+		}
+		updatedClientIDs = append(updatedClientIDs, clientID)
+	}
+	return nil
+}
+
+func rollbackClientsMFAChain(ctx context.Context, st storage.Storage, clientIDs []string, previousChains map[string][]string) error {
+	var rollbackErrs []error
+	for i := len(clientIDs) - 1; i >= 0; i-- {
+		clientID := clientIDs[i]
+		previousChain := cloneMFAChain(previousChains[clientID])
+		if err := st.UpdateClient(ctx, clientID, func(old storage.Client) (storage.Client, error) {
+			old.MFAChain = previousChain
+			return old, nil
+		}); err != nil {
+			rollbackErrs = append(rollbackErrs, fmt.Errorf("client %s: %w", clientID, err))
+		}
+	}
+	return errors.Join(rollbackErrs...)
+}
+
+func cloneMFAChain(chain []string) []string {
+	if chain == nil {
+		return nil
+	}
+	return append([]string(nil), chain...)
+}
+
 // SetClientsMFAChain updates the MFAChain field on the dashboard and CLI OAuth2 clients.
 // Pass a non-empty slice (e.g. []string{"default-totp"}) to enable MFA, or nil to disable it.
 func (p *Provider) SetClientsMFAChain(ctx context.Context, clientIDs []string, mfaChain []string) error {
-	for _, clientID := range clientIDs {
-		if err := p.storage.UpdateClient(ctx, clientID, func(old storage.Client) (storage.Client, error) {
-			old.MFAChain = mfaChain
-			return old, nil
-		}); err != nil {
-			return fmt.Errorf("failed to update MFA chain on client %s: %w", clientID, err)
-		}
-	}
-	return nil
+	return SetClientsMFAChain(ctx, p.storage, clientIDs, mfaChain)
 }
 
 // Handler returns the Dex server as an http.Handler for embedding in another server.
@@ -545,7 +587,7 @@ func (p *Provider) CreateUser(ctx context.Context, email, username, password str
 
 	// Encode the user ID in Dex's format: base64(protobuf{user_id, connector_id})
 	// This matches the format Dex uses in JWT tokens
-	encodedID := EncodeDexUserID(userID, localConnectorID)
+	encodedID := EncodeDexUserID(userID, LocalConnectorID)
 	return encodedID, nil
 }
 
@@ -624,7 +666,7 @@ func DecodeDexUserID(encodedID string) (userID, connectorID string, err error) {
 // local password connector.
 func IsLocalUserID(encodedID string) bool {
 	_, connectorID, err := DecodeDexUserID(encodedID)
-	return err == nil && connectorID == localConnectorID
+	return err == nil && connectorID == LocalConnectorID
 }
 
 // GetUser returns a user by email

idp/dex/provider_test.go

@@ -3,6 +3,8 @@ package dex
 import (
 	"context"
 	"encoding/json"
+	"errors"
+	"io"
 	"log/slog"
 	"net/http"
 	"net/http/httptest"
@@ -11,11 +13,44 @@ import (
 	"testing"
 
 	"github.com/dexidp/dex/storage"
+	"github.com/dexidp/dex/storage/memory"
 	sqllib "github.com/dexidp/dex/storage/sql"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
+type updateFailingStorage struct {
+	storage.Storage
+	failClientID string
+}
+
+func (s *updateFailingStorage) UpdateClient(ctx context.Context, id string, updater func(storage.Client) (storage.Client, error)) error {
+	if id == s.failClientID {
+		return errors.New("forced update failure")
+	}
+	return s.Storage.UpdateClient(ctx, id, updater)
+}
+
+func TestSetClientsMFAChainRollsBackUpdatedClients(t *testing.T) {
+	ctx := context.Background()
+	st := memory.New(slog.New(slog.NewTextHandler(io.Discard, nil)))
+
+	require.NoError(t, st.CreateClient(ctx, storage.Client{ID: "client-1", MFAChain: []string{"old-1"}}))
+	require.NoError(t, st.CreateClient(ctx, storage.Client{ID: "client-2", MFAChain: []string{"old-2"}}))
+
+	err := SetClientsMFAChain(ctx, &updateFailingStorage{Storage: st, failClientID: "client-2"}, []string{"client-1", "client-2"}, []string{"new"})
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "failed to update MFA chain on client client-2")
+
+	client1, err := st.GetClient(ctx, "client-1")
+	require.NoError(t, err)
+	require.Equal(t, []string{"old-1"}, client1.MFAChain)
+
+	client2, err := st.GetClient(ctx, "client-2")
+	require.NoError(t, err)
+	require.Equal(t, []string{"old-2"}, client2.MFAChain)
+}
+
 func TestUserCreationFlow(t *testing.T) {
 	ctx := context.Background()