feat(web): series, season and episode removal

Series detail exposes DELETE /api/series/{id} through the movie
removePanel, generalised over endpoints and file rollup instead of
copied. Season headers and on-disk episode rows get the settings
armed-delete control wired to #174's file endpoints, worded for what
they do: files go, wanted clears, the row stays listed.

Closes #175

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

web/index.html

@@ -495,6 +495,28 @@
         </div>
       </section>
 
+      <!-- removal is the one library control a series carries (issue 175):
+           the same arming panel a movie uses — evidence first, then the
+           decision — wired to DELETE /api/series/{id} -->
+      <section class="deck-group" id="series-library" aria-label="library controls">
+        <header class="deck-head">
+          <h3 class="deck-label">library</h3>
+        </header>
+        <div class="movie-controls">
+          <span class="movie-controls-space"></span>
+          <button
+            type="button"
+            class="control control-quiet"
+            id="series-remove"
+            aria-expanded="false"
+            aria-controls="series-remove-panel"
+          >
+            remove
+          </button>
+        </div>
+        <div class="remove-panel" id="series-remove-panel" hidden></div>
+      </section>
+
       <ul class="deck-rows seasons" id="rows-seasons"></ul>
     </main>