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>

internal/api/auth_forgot.go

@@ -133,7 +133,7 @@ func (h *handlers) sendResetEmail(ctx context.Context, user dbq.User) error {
 // errNoPublicURL stops a reset email from going out before the operator has
 // said where Minstrel lives. It surfaces in the log, not the response, which
 // stays the same opaque 200 either way.
-var errNoPublicURL = errors.New("forgot-password: no public URL set (Admin → Integrations → Public address); reset email not sent")
+var errNoPublicURL = errors.New("forgot-password: no public URL set (Admin › Email & network › Public address); reset email not sent")
 
 // buildResetURL builds the emailed link from the operator-set public URL.
 // It deliberately ignores the request: the Host header is whatever the