merge: Android runtime security (B1, B3)

Correct the POST_NOTIFICATIONS mechanism: the lockscreen notification is exempt
because of the MediaSession token, not because it belongs to a foreground
service — FGS notifications are explicitly NOT exempt. So no permission prompt
and no checkSelfPermission gate; instead both notification builders bind the
token once and log loudly if it is ever null, turning a silent failure into a
logcat line. Stop the webview undoing the network security config:
mixedContentMode COMPATIBILITY, allowFileAccess/allowContentAccess false.

Conflict resolution: this branch's DR-198 collided with the Tauri branch's, so
it was renumbered DR-200 (3 TRACES in JellyTauPlaybackService.kt and the UR-006
matrix row updated). DR-199 was uncontested. Pinned counts summed to DR 191 /
total 334; UR-071 takes both DR-198 and DR-199.

docs/architecture/09-security.md

@@ -50,6 +50,8 @@ pub struct EncryptedFileStorage; // AES-256-GCM fallback
 | Certificate Validation | System CA store (configurable for self-signed) |
 | Token Transmission | Bearer token in `Authorization` header only |
 | Token Refresh | Handled by Jellyfin server (long-lived tokens) |
+| Android cleartext | `res/xml/network_security_config.xml` blocks cleartext everywhere except `127.0.0.1` (the loopback media server, DR-137/DR-138). The manifest's `usesCleartextTraffic` is ignored once the config is present, so the config is the single authority |
+| Android WebView | `mixedContentMode = COMPATIBILITY` with `allowFileAccess`/`allowContentAccess` both `false` (DR-199). These are the second half of the cleartext policy: `ALWAYS_ALLOW` re-opened by hand what the network security config closes. Change the two together |
 
 ## Webview Content Security Policy