docs: prune redundant Networks and Network Routes use cases (#749)

The Networks and Network Routes "By Scenario" / "By Resource Type" /
"By Configuration" subgroups had grown into reskinned walkthroughs of
flows already on the concept pages. Collapse to what's actually
distinct, flatten the survivors up one level, fold unique nuggets
into the concept pages.

Networks:
- Delete the "By Resource Type" trio (Multiple IP Resources, Domain
  Resources, Wildcard Domains) and Remote Worker Access — all rehashes
  of /manage/networks. Fold the wildcard-vs-base-domain gotcha and the
  shared-policy pattern into the concept page.
- Delete the Use Cases overview; fold the VPN-to-Site framing into the
  concept page.
- Flatten access-home-devices and cloud-to-on-premise up out of
  /by-scenario/.

Network Routes:
- Consolidate site-to-site-{home,office,cloud} into one
  /manage/network-routes/use-cases/site-to-site page covering the
  shared walkthrough plus AWS/GCP/Azure routing-peer requirements.
- Move exit-nodes, access-control, overlapping-routes, and
  advanced-configuration up out of /by-{scenario,configuration}/.
- Trim advanced-configuration (301 → 144 lines), dropping masquerade
  basics, ACL setup, site-to-site flow, and HA repetition duplicated
  elsewhere. Keep the masquerade trade-off matrix, Networks-vs-Routes
  comparison, troubleshooting, and debug commands.
- Delete the Use Cases overview.

Permanent redirects added for every removed URL. Inbound references
updated across introduction, ipv6, homelab, cloud, security,
site-to-site overview, android-tv/tvOS install pages, and the concept
pages.

src/pages/get-started/install/android-tv.mdx

@@ -81,6 +81,6 @@ the SSO flow, the QR code dialog in the NetBird app will automatically dismiss i
 
 ## What's next?
 - Manage your device's [access](/manage/access-control/manage-network-access) to the network
-- Use your device for [remote access access to your home network](/manage/networks/use-cases/by-scenario/access-home-devices)
-- Use your device as an [exit node](/manage/network-routes/use-cases/by-scenario/exit-nodes#make-the-peer-an-exit-node-routing-peer)
+- Use your device for [remote access access to your home network](/manage/networks/use-cases/access-home-devices)
+- Use your device as an [exit node](/manage/network-routes/use-cases/exit-nodes#make-the-peer-an-exit-node-routing-peer)
 

src/pages/get-started/install/tvos.mdx

@@ -54,5 +54,5 @@ the SSO flow, after a few seconds the authentication dialog in the NetBird app w
 
 ## What's next?
 - Manage your device's [access](/manage/access-control/manage-network-access) to the network
-- Use your device for [remote access access to your home network](/manage/networks/use-cases/by-scenario/access-home-devices)
-- Use your device as an [exit node](/manage/network-routes/use-cases/by-scenario/exit-nodes#make-the-peer-an-exit-node-routing-peer)
+- Use your device for [remote access access to your home network](/manage/networks/use-cases/access-home-devices)
+- Use your device as an [exit node](/manage/network-routes/use-cases/exit-nodes#make-the-peer-an-exit-node-routing-peer)