feat(downloads): pause and resume support for the download manager (#1147)

Adds a paused state to the Electron download manager with a full partial-file lifecycle:

- Pause keeps the .part and byte progress; cancel discards them; every lifecycle stage (queued, active, mid-transfer) is pausable.
- Resume continues via HTTP Range with If-Range entity validation (strong ETag / Last-Modified persisted in the new resume_validator column, idempotent migration incl. legacy-table rebuild). Non-206 answers restart from zero over the same .part; the 206 Content-Range offset is verified; responses that end before the advertised size are retained for a Range retry instead of being committed as completed.
- Crash recovery converts interrupted transfers to paused, keeps queued-with-partial rows resumable, and commits finalizations that crashed before the DB update.
- Destination collisions are non-destructive (retained partials finalize to the next numbered name); locked .part files never lose their DB owner across cancel/remove/restart; resume claims rows atomically and the queue dedupes ids.
- Stored request headers are re-filtered through the User-Agent/Origin/Referer allowlist on read, URL-derived extensions are sanitized, resume appends never follow symlinks, and transfer errors are logged by message only.
- UI: pause/resume/cancel/retry/remove surface failures in a snackbar; paused items show an active Resume button in VOD/episode detail views; translations for all 18 locales.
- Runtime split into download-runtime/transfer/finalize/broadcast modules; +30 unit tests and an Electron E2E covering pause -> retained .part -> Range/If-Range resume -> byte-exact assembly.

Co-authored-by: genrichh93-ui <genrichh93@users.noreply.github.com>
🤖 Generated with [Claude Code](https://claude.com/claude-code)

libs/shared/interfaces/src/lib/electron-api.interface.ts

@@ -119,6 +119,7 @@ export const ELECTRON_BRIDGE_DOWNLOAD_STATUSES = {
     Completed: 'completed',
     Downloading: 'downloading',
     Failed: 'failed',
+    Paused: 'paused',
     Queued: 'queued',
 } as const;
 
@@ -953,6 +954,11 @@ export interface ElectronBridgeApi {
         data: ElectronBridgeDownloadStartPayload
     ) => Promise<ElectronBridgeDownloadStartResult>;
     downloadsCancel: (downloadId: number) => Promise<ElectronBridgeErrorResult>;
+    downloadsPause: (downloadId: number) => Promise<ElectronBridgeErrorResult>;
+    downloadsResume: (
+        downloadId: number,
+        downloadFolder: string
+    ) => Promise<ElectronBridgeErrorResult>;
     downloadsRetry: (
         downloadId: number,
         downloadFolder: string