domain: player/reporting ticks -> milliseconds (phase 4c)

Playback position now crosses the IPC boundary in milliseconds. Ticks
survive only inside Rust (DB storage, Jellyfin API) and at the genuine
remote-session boundary (session seek / transfer / RemoteControls).

Rust command signatures (ms in, converted to ticks internally):
- storage_update_playback_progress / _context: position_ms
- repository_report_playback_start / _progress / _stopped: position_ms
- PlaybackProgress.position_ticks -> position_ms (converted in the query)

Frontend:
- playbackReporting, playerEvents, VideoPlayer, Queue, player/[id] resume:
  seconds*1000 / durationMs/1000 instead of tick math.
- repository-client + syncService param names -> positionMs.
- Tests updated to ms fixtures/assertions.

Out of scope (legitimately ticks): NowPlayingItem, PlayState.positionTicks,
sessionSeek, playbackModeTransferToLocal, RemoteControls, SessionCard — the
remote Jellyfin session API.

Rust 456, frontend 644, check clean.

src/lib/api/repository-client.ts

@@ -164,16 +164,16 @@ export class RepositoryClient {
     return commands.repositoryGetPlaybackInfo(this.ensureHandle(), itemId);
   }
 
-  async reportPlaybackStart(itemId: string, positionTicks: number): Promise<void> {
-    await commands.repositoryReportPlaybackStart(this.ensureHandle(), itemId, positionTicks);
+  async reportPlaybackStart(itemId: string, positionMs: number): Promise<void> {
+    await commands.repositoryReportPlaybackStart(this.ensureHandle(), itemId, positionMs);
   }
 
-  async reportPlaybackProgress(itemId: string, positionTicks: number): Promise<void> {
-    await commands.repositoryReportPlaybackProgress(this.ensureHandle(), itemId, positionTicks);
+  async reportPlaybackProgress(itemId: string, positionMs: number): Promise<void> {
+    await commands.repositoryReportPlaybackProgress(this.ensureHandle(), itemId, positionMs);
   }
 
-  async reportPlaybackStopped(itemId: string, positionTicks: number): Promise<void> {
-    await commands.repositoryReportPlaybackStopped(this.ensureHandle(), itemId, positionTicks);
+  async reportPlaybackStopped(itemId: string, positionMs: number): Promise<void> {
+    await commands.repositoryReportPlaybackStopped(this.ensureHandle(), itemId, positionMs);
   }
 
   // ===== Stream URL Methods (via Rust) =====