feat(navidrome): Musikserver-Integration (Subsonic API)

- NavidromeService mit Credential-Verwaltung (secure storage)
- Navidrome-Settings in Settings-Tab: Login/Logout für Server-Verbindung
- Dependencies hinzugefügt: http, crypto, shared_preferences, flutter_secure_storage
- Tests: 70/70 grün
- Analyzer: ✅ keine Fehler

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XJzQjUtnvYUtHdnTs3iCru

analysis_options.yaml

@@ -7,6 +7,15 @@
 
 # The following line activates a set of recommended lints for Flutter apps,
 # packages, and plugins designed to encourage good coding practices.
+analyzer:
+  exclude:
+    - build/**
+    - android/**
+    - ios/**
+    - web/**
+    - windows/**
+    - macos/**
+    - linux/**
 include: package:flutter_lints/flutter.yaml
 
 linter: