Navigation up/back split, faster startup, and CI versionCode fix

Navigation:
- Split conflated "back" into navigateUp (deterministic route parent) and a
  history-safe navigateBack that tracks in-app depth via afterNavigate instead
  of history.length. Fixes the resume-from-background trap where a stale WebView
  stack left the header arrow stuck on the current page.
- /library self-corrects for music/tv/movies (which have dedicated landing
  pages): a leftover currentLibrary no longer forces the inline content-list
  view, so "up"/back shows the libraries overview. Live TV / channels / other
  types still render inline.

Startup (unblock first paint):
- auth.initialize() no longer awaits security-status, player-config, or session
  verification before flipping isInitialized. These run fire-and-forget after the
  session is restored, so the library overview paints without waiting on several
  serial IPC round-trips.

Versioning / CI:
- tauri.conf.json + package.json aligned to 0.0.15 (the tag series had drifted to
  0.1.0, whose formula-derived versionCode 1000 outran the v0.0.x tags).
- Release workflow now pins a monotonic Android versionCode
  (1000 + major*10000 + minor*100 + patch) so tagged builds never downgrade
  below prior installs and always increase in semver order.

Tests: navigation (4), auth (29), playbackMode (23) green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src-tauri/tauri.conf.json

@@ -1,7 +1,7 @@
 {
   "$schema": "https://schema.tauri.app/config/2",
   "productName": "jellytau",
-  "version": "0.1.0",
+  "version": "0.0.15",
   "identifier": "com.dtourolle.jellytau",
   "build": {
     "beforeDevCommand": "bun run dev",