Resolution dropdown, list-focus preservation, unified dark theme, startup logging, and memory map

- Bottom-bar resolution dropdown (1080p60/1080p30/720p60/480p30) with tooltip
  on finding upload bandwidth; disabled while live; no in-app speed test
- FocusPreservingListBox keeps selection/focus coherent when a selected
  scene/source is deleted (skip hidden scenes; leave list when empty)
- Themes/Controls.xaml: single dark-theme dictionary merged once in App.xaml;
  custom ComboBox template fixes SelectionBoxItem rendering; GoLiveWindow and
  ReuseImageDialog consolidated onto shared styles
- AppLog file logger + AppDomain/Dispatcher exception hooks; checkpointed
  MainWindow/VM/dialog constructors (caught MenuItemRole.Separator XAML crash)
- Memory map: schema.md conventions, per-directory index.md, updated ai.md/
  TASKS.md/README.md (OAuth creds real; token persistence still pending)

Services/index.md

@@ -0,0 +1,15 @@
+# Services — index
+
+External-facing logic: YouTube API, persistence. See
+[`schema.md`](../schema.md) for the memory-map conventions.
+
+| File | Purpose |
+|------|---------|
+| `YouTubeAuthService.cs` | OAuth2 via Google: loopback callback (`http://localhost:8765/oauth2/callback`), token exchange, refresh, channel fetch. **Complete — but no token persistence yet** (DPAPI planned) |
+| `YouTubeStreamService.cs` | Broadcast/stream management via the v3 API (`enableAutoStart/Stop`). **Not yet switched to the `variable` reusable stream** |
+| `YouTubeChatService.cs` | Polls `liveChat/messages`, raises `MessageReceived`; `IDisposable` |
+| `LayoutStore.cs` | SQLite persistence (`Microsoft.Data.Sqlite`) at `%APPDATA%\ytLlive\ytLlive.db`; assets stored as BLOBs keyed by SHA-256 content hash; save/open layout files |
+
+Related: constructed in [`ViewModels/MainViewModel.cs`](../ViewModels/MainViewModel.cs)
+(no DI container yet). Models in [`Models/index.md`](../Models/index.md).
+OAuth credentials live in [`Helpers/OAuthCredentials.cs`](../Helpers/OAuthCredentials.cs).