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/ui/components/src/lib/season-container/season-container.component.html

@@ -173,6 +173,25 @@
                                             >
                                                 <mat-icon>play_circle</mat-icon>
                                             </button>
+                                        } @else if (
+                                            isEpisodePaused(episode)
+                                        ) {
+                                            <button
+                                                mat-icon-button
+                                                class="download-btn download-btn--paused"
+                                                (click)="
+                                                    resumeEpisodeDownload(
+                                                        $event,
+                                                        episode
+                                                    )
+                                                "
+                                                [matTooltip]="
+                                                    'DOWNLOADS.RESUME'
+                                                        | translate
+                                                "
+                                            >
+                                                <mat-icon>play_arrow</mat-icon>
+                                            </button>
                                         } @else if (
                                             isEpisodeDownloading(episode)
                                         ) {
@@ -413,6 +432,22 @@
                                         >
                                             <mat-icon>folder_open</mat-icon>
                                         </button>
+                                    } @else if (isEpisodePaused(episode)) {
+                                        <button
+                                            mat-icon-button
+                                            class="action-btn"
+                                            (click)="
+                                                resumeEpisodeDownload(
+                                                    $event,
+                                                    episode
+                                                )
+                                            "
+                                            [matTooltip]="
+                                                'DOWNLOADS.RESUME' | translate
+                                            "
+                                        >
+                                            <mat-icon>play_arrow</mat-icon>
+                                        </button>
                                     } @else if (isEpisodeDownloading(episode)) {
                                         <button
                                             mat-icon-button

libs/ui/components/src/lib/season-container/season-container.component.scss

@@ -394,6 +394,14 @@ app-season-tabs {
             color: rgba(255, 255, 255, 0.5) !important;
             cursor: not-allowed;
         }
+
+        .download-btn--paused {
+            color: #fbbf24 !important;
+
+            &:hover {
+                background: color-mix(in srgb, #fbbf24 20%, transparent);
+            }
+        }
     }
 
     &:hover {

libs/ui/components/src/lib/season-container/season-container.component.ts

@@ -414,6 +414,35 @@ export class SeasonContainerComponent implements OnInit {
         );
     }
 
+    isEpisodePaused(episode: XtreamSerieEpisode): boolean {
+        if (!this.playlistId()) {
+            return false;
+        }
+
+        this.downloadsService.downloads();
+        return this.downloadsService.isPaused(
+            getEpisodeDownloadId(episode),
+            this.playlistId(),
+            'episode'
+        );
+    }
+
+    async resumeEpisodeDownload(
+        event: Event,
+        episode: XtreamSerieEpisode
+    ): Promise<void> {
+        event.stopPropagation();
+        if (!this.playlistId()) {
+            return;
+        }
+
+        await this.downloadsService.resumeDownloadByContent(
+            getEpisodeDownloadId(episode),
+            this.playlistId(),
+            'episode'
+        );
+    }
+
     async playFromLocal(event: Event, episode: XtreamSerieEpisode) {
         event.stopPropagation();
         if (!this.playlistId()) {