feat(api,web): remove a movie, files optional

`DELETE /api/movies/{id}` took the row and left the files, and no
surface exposed it. It now accepts `delete_files`, which unlinks the
title's §7.4 folder — atomic, so sidecars go with the feature. Targets
come from `media_files`, never from re-deriving the folder name, and a
path outside its root is never touched. The torrent is untouched (§7.3):
it keeps seeding and the reaper owns it.

The release deck grows a quiet REMOVE control opening one inline
confirmation: file count, size and folder first, then a delete-files
toggle that starts off, then what the choice costs.

Closes #104

.sqlx/query-8acc97e569480889f051e71a38e52413c707001e86aeb8ef94131d522690ffdf.json

@@ -0,0 +1,12 @@
+{
+  "db_name": "SQLite",
+  "query": "DELETE FROM title_owners WHERE title_kind = 'movie' AND title_id = ?",
+  "describe": {
+    "columns": [],
+    "parameters": {
+      "Right": 1
+    },
+    "nullable": []
+  },
+  "hash": "8acc97e569480889f051e71a38e52413c707001e86aeb8ef94131d522690ffdf"
+}