feat: Integrations splits into Library, Acquisition, Metadata sources and Email & network, each a page on the admin rail; the Overview keeps only what needs you (M503 #5607)

- Library: the folders, Run scan and a row per scan job, cover art, fingerprints and loudness (off the Overview and Duplicates)
- Acquisition: indexers and clients, searching, re-acquisition (off Missing files), Lidarr
- Metadata sources: AcoustID, and one provider block for cover art and tags in place of the pasted pair
- Email & network: outgoing email, the notification schedule, public address, proxies
- Lidarr, outgoing email and the provider block are rebuilt as SettingsGroup rows; failures read as sentences, not codes
- Duplicates and Missing files say what their setting is and link to where it is set

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/hosting.md

@@ -13,7 +13,7 @@ Publish the port to the network and use `http://<host>:4533`:
     ports: ['4533:4533']
 ```
 
-If nothing sits in front of Minstrel, set **Admin → Integrations → Client IP
+If nothing sits in front of Minstrel, set **Admin › Email & network → Client IP
 detection** to 0. It defaults to 1, which assumes one proxy (see below for
 why that matters).
 
@@ -48,7 +48,7 @@ Three things, all required:
      the app is. Raise the proxy's read timeout well past a minute (nginx:
      `proxy_read_timeout 1h;`).
 
-3. **Tell Minstrel where it lives**, in **Admin → Integrations**:
+3. **Tell Minstrel where it lives**, in **Admin › Email & network**:
    - **Client IP detection:** the number of proxies in front of Minstrel. One
      proxy (Caddy, Traefik, nginx) is 1; Cloudflare in front of Traefik is 2.
      Minstrel uses this to find the real client address, for login rate

docs/screenshots/README.md

@@ -11,7 +11,7 @@ across all shots for a consistent look.
 | `home.png` | `/` | The home page with a populated library (system playlists / recently added) |
 | `register.png` | `/register` | The account-creation form on a fresh instance |
 | `library-scan.png` | `/admin` | The library scan running in stages (grab it mid-scan so stage tallies show) |
-| `integrations.png` | `/admin/integrations` | The ListenBrainz + Lidarr integration cards |
+| `integrations.png` | `/admin/acquisition` | Indexers, download clients, searching and Lidarr |
 | `android-download.png` | `/settings` | The "Install the Android app" download card |
 | `invite-users.png` | `/admin/users` | The invite-token generation / users list |