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/lidarr/types.go

@@ -25,7 +25,7 @@ type lidarrImage struct {
 	URL       string `json:"url"`
 }
 
-// QualityProfile is the dropdown choice in /admin/integrations.
+// QualityProfile is the dropdown choice on Admin › Acquisition.
 type QualityProfile struct {
 	ID   int
 	Name string
@@ -41,7 +41,7 @@ type MetadataProfile struct {
 	Name string
 }
 
-// RootFolder is the dropdown choice in /admin/integrations.
+// RootFolder is the dropdown choice on Admin › Acquisition.
 type RootFolder struct {
 	Path       string
 	Accessible bool