fix(media-keys): withdraw paused session on blur, dedup SMTC pushes, sanitize titles, decode Xtream names

[Thunderhawkk]

Summary

Fixes Harbor hijacking OS media keys (Windows SMTC / Linux MPRIS) from other apps. Five files, no refactors:

• src-tauri/.../media_controls.rs (Windows): update() now skips identical pushes via a last-pushed cache, so background/paused Harbor stops bumping itself to most-recent; pushed titles are trimmed, control-char-filtered, and length-capped.
• src/lib/media-session.ts: new isMediaSessionActive gate, force re-push option, and setMediaSessionWindowFocused — a paused session is withdrawn when the window loses focus and re-asserted on refocus; ended/unmount clears permanently.
• src/views/player.tsx: media-controls effect clears on ended/idle/error (not just unmount), clock ticks re-check the gate, focus changes route to the policy function. Key handling (toggle/next/previous) untouched.
• src/lib/iptv/xtream.ts, xtream-vod.ts: live/VOD/series names go through the existing defensive decodeBase64 (plain names pass through unchanged), so provider-encoded names no longer reach the flyout as eyJ... garbage.

Why

A paused/background Harbor kept an enabled OS session and re-announced it, so Windows routed Play/Pause to Harbor instead of the active app (Harbor resumed while Spotify paused — same failure class as known Spotify-vs-YouTube reports). Ended playback never cleared the session, leaving dead entries whose keys did nothing. The VLC-style approach (no enabled session while paused-and-unfocused, keep it while playing in background, reclaim on refocus) fits Harbor because playback, background listening, and hotkeys keep working exactly as before — only session advertisement changes.

Verification

• Adjacent suites (interaction-lock, buffer-policy, mouse-hold, subtitle-fps, critical-path, focus-resume, lifecycle, unlisten): 62/62 pass.
• pnpm run typecheck (tsc -b): clean. cargo check: clean

Platform Impact

• Windows: SMTC push dedup + title sanitization + withdraw-on-blur-while-paused; the reported hijack and garbage-title cases.
• Linux: same frontend withdraw/re-assert policy applies to the MPRIS session (clear → Stopped unchanged); MPRIS already diffs before signaling.

Checklist

• This pull request is focused and contains no unrelated refactors.
• I ran vp check for the changed files.
• I ran vp run typecheck after TypeScript changes.
• I ran the relevant Cargo checks after Rust changes.
• I tested affected platforms when the change is platform-specific.
• I preserved playback, navigation, and configured hotkey behavior where applicable.
• I added or updated tests for behavior changes.
• I removed secrets, tokens, private URLs, and personal data from logs and screenshots.