feat(cdn): integrate CDN Manager into the application

- Updated environment configurations to include CDN Manager in the RETURN_TO_ALLOWLIST.
- Enhanced target app resolution to recognize CDN-related hosts.
- Added CDN Manager to the application switcher and updated relevant documentation.
- Included tests to verify the correct mapping of CDN hosts.

Co-authored-by: Cursor <cursoragent@cursor.com>

deploy/env.traefik.example

@@ -24,7 +24,7 @@ ADMIN_EMAIL=admin@shnt.top
 ADMIN_PASSWORD=
 ADMIN_NAME=Admin
 # Include Technitium origin if used (e.g. https://dns.shnt.top)
-RETURN_TO_ALLOWLIST=.shnt.top,https://vps.shnt.top,https://cfdm.shnt.top,https://bgp.shnt.top,https://fw.shnt.top,https://dns.shnt.top
+RETURN_TO_ALLOWLIST=.shnt.top,https://vps.shnt.top,https://cfdm.shnt.top,https://bgp.shnt.top,https://fw.shnt.top,https://dns.shnt.top,https://cdn.shnt.top
 LOG_LEVEL=info
 NODE_ENV=production
 # WebAuthn / passkeys (defaults from ISSUER hostname + origin)