[management] Rework Agent Network endpoint identity and settings bootstrap (#7085)

Store the per-account gateway endpoint as {domain, proxy_address} with a
global unique index on the full hostname; dedicated = (domain ==
proxy_address). Bootstrap becomes an explicit POST carrying exactly one
of proxy_address (server allocates an adjective-noun label beneath it)
or endpoint (claimed verbatim, address-first); provider create loses its
bootstrap side effect. PUT is a full replace with every field required —
the immutable identity fields must be echoed unchanged and a mismatch is
rejected with 422. A guarded DELETE releases the endpoint: refused with
412 while providers exist or a proxy is actively serving the endpoint
hostname (matched case-insensitively); re-creating bootstraps fresh. A
self-addressed pin excludes its address from the account's cluster allow
list, and the live mapping update path now addresses the serving proxy
from the synthesized service. Existing rows are migrated on all three
store engines.

e2e/harness/agentnetwork.go

@@ -126,17 +126,33 @@ func (c *Combined) DeleteGuardrail(ctx context.Context, id string) error {
 	return anDelete(ctx, c, "/api/agent-network/guardrails/"+id)
 }
 
-// GetSettings returns the account's agent-network settings row. It exists only
-// after the first provider create bootstraps it.
+// CreateSettings bootstraps the account's agent-network settings row,
+// assigning the immutable endpoint. Exactly one of req.ProxyAddress (labeled
+// endpoint beneath that cluster) and req.Endpoint (self-addressed dedicated
+// endpoint) must be set; a second bootstrap returns a conflict.
+func (c *Combined) CreateSettings(ctx context.Context, req api.AgentNetworkSettingsCreateRequest) (api.AgentNetworkSettings, error) {
+	return anRequest[api.AgentNetworkSettings](ctx, c, http.MethodPost, "/api/agent-network/settings", req)
+}
+
+// GetSettings returns the account's agent-network settings row. Before the
+// CreateSettings bootstrap it reads as the defaults with an empty endpoint.
 func (c *Combined) GetSettings(ctx context.Context) (api.AgentNetworkSettings, error) {
 	return anRequest[api.AgentNetworkSettings](ctx, c, http.MethodGet, "/api/agent-network/settings", nil)
 }
 
-// UpdateSettings applies the mutable collection toggles.
+// UpdateSettings applies the mutable collection toggles. The request must
+// echo the assigned endpoint and proxy address unchanged — the server rejects
+// a PUT that tries to change them.
 func (c *Combined) UpdateSettings(ctx context.Context, req api.AgentNetworkSettingsRequest) (api.AgentNetworkSettings, error) {
 	return anRequest[api.AgentNetworkSettings](ctx, c, http.MethodPut, "/api/agent-network/settings", req)
 }
 
+// DeleteSettings removes the account's settings row, releasing the endpoint.
+// Refused while providers exist or a proxy is actively serving the endpoint.
+func (c *Combined) DeleteSettings(ctx context.Context) error {
+	return anDelete(ctx, c, "/api/agent-network/settings")
+}
+
 // ListConsumption returns the account's consumption rows (possibly empty).
 func (c *Combined) ListConsumption(ctx context.Context) ([]api.AgentNetworkConsumption, error) {
 	return anRequest[[]api.AgentNetworkConsumption](ctx, c, http.MethodGet, "/api/agent-network/consumption", nil)