feat(admin): multi-select episode file deletion — checkboxes on downloaded rows

The plan's per-EPISODE bulk select for the admin view (§0 item 8
follow-up — trimmed in the first admin-view commit; user called it
back). Admins now tick checkboxes on DOWNLOADED episode rows and delete
their files in one request:

- Checkbox per row, rendered ONLY for admins + downloaded episodes
  (nothing to delete otherwise), via the existing podcastDetail Alpine
  component: selection ids/count survive the list's htmx swaps
  (reapplied on afterSwap — same pattern as the text filter) and clear
  after a successful bulk delete.
- Toolbar segment outside #episode-list (survives swaps): 'N selected'
  + 'Delete selected files' (hx-include gathers the CHECKED boxes);
  disabled-looking at zero selection; hx-confirm states the
  re-materialization contract. CSP-safe method bindings only
  (bulkSelectionLabel/Class) — no ternaries in Alpine expressions.
- POST /feeds/:id/episodes/delete-files (admin): repeated
  episode-file-select keys parsed via ParseForm directly (never bound —
  repeated-key wire is another echo-bind gotcha); each id validated to
  belong to THIS feed, so a forged foreign id is refused while the real
  selections apply; rows reset to pending, files removed.
- Tests: bulk of two real ids + one forged id → deleted:2, files gone,
  rows pending; non-admin 403; all prior single/feed-level pins hold.

templates/podcast_detail.templ

@@ -240,6 +240,31 @@ templ PodcastDetailPage(user User, data PodcastDetailData) {
 						Hide played/downloaded
 					</label>
 					<span class="text-xs hidden" x-ref="filterEmptyNote" style="color: var(--text-secondary)">No episodes match the filter.</span>
+
+					<!-- Admin bulk file deletion (§0 item 8 follow-up): the
+					     transport for the per-row checkboxes inside the episode
+					     list. Lives OUTSIDE #episode-list so the button survives
+					     the list's htmx swaps; hx-include gathers the CHECKED
+					     boxes into the post body. State (count/ids) lives in the
+					     podcastDetail component — CSP-safe method bindings only. -->
+					if data.IsAdmin && data.Feed.DownloadedN > 0 {
+						<div class="ml-auto flex items-center gap-2">
+							<span class="text-xs tabular-nums" style="color: var(--text-secondary)" x-text="bulkSelectionLabel()"></span>
+							<button
+								id="episode-bulk-delete"
+								type="button"
+								class="btn btn-secondary text-xs"
+								:class="bulkSelectionClass()"
+								hx-post={ "/api/podcasts/feeds/" + data.Feed.ID + "/episodes/delete-files" }
+								hx-include="input[name='episode-file-select']:checked"
+								hx-swap="none"
+								hx-confirm="Delete the selected episode files? Rows reset to pending (a feed refresh will not re-materialize them); episodes re-download on demand."
+								style="color: var(--status-warning, #d97706);"
+							>
+								Delete selected files
+							</button>
+						</div>
+					}
 				</div>
 
 				<!-- Episode list (self-refreshing htmx partial). Pick the
@@ -277,7 +302,7 @@ templ PodcastEpisodeList(data PodcastDetailData) {
 		} else {
 			<div class="flex flex-col gap-2">
 				for _, ep := range data.Episodes {
-					@PodcastEpisodeRowView(ep)
+					@PodcastEpisodeRowView(ep, data.IsAdmin)
 				}
 			</div>
 		}
@@ -297,13 +322,13 @@ templ PodcastEpisodeListPolling(data PodcastDetailData) {
 		<h2 class="text-lg font-bold mb-3" style="color: var(--text-primary)">Episodes</h2>
 		<div class="flex flex-col gap-2">
 			for _, ep := range data.Episodes {
-				@PodcastEpisodeRowView(ep)
+				@PodcastEpisodeRowView(ep, data.IsAdmin)
 			}
 		</div>
 	</div>
 }
 
-templ PodcastEpisodeRowView(ep PodcastEpisodeRow) {
+templ PodcastEpisodeRowView(ep PodcastEpisodeRow, isAdmin bool) {
 	<div
 		class="card p-3 flex items-center gap-3"
 		data-episode-row="true"
@@ -311,6 +336,26 @@ templ PodcastEpisodeRowView(ep PodcastEpisodeRow) {
 		data-listen-pct={ podcastPct(ep.ListenPct) }
 		data-search-text={ strings.ToLower(ep.Title + " " + ep.Description) }
 	>
+		<!-- Admin bulk-select (§0 item 8 follow-up): multi-select
+		     downloaded episodes for file deletion. Rendered ONLY for
+		     admins + DOWNLOADED rows — a checkbox on a file-less episode
+		     would be an invitation to confusion. State survives the
+		     list's htmx swaps via the podcastDetail component
+		     (reapplied on afterSwap). -->
+		if isAdmin {
+			if ep.Downloaded {
+				<input
+					type="checkbox"
+					name="episode-file-select"
+					value={ ep.ID }
+					class="cursor-pointer shrink-0"
+					aria-label={ "Select " + ep.Title + " for file deletion" }
+					@change="toggleBulkSelection($event.target)"
+				/>
+			} else {
+				<span class="w-4 shrink-0"></span>
+			}
+		}
 		<span class="text-xs font-mono w-10 shrink-0 text-right" style="color: var(--text-secondary)">
 			{ podcastInt(ep.Position) }
 		</span>