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-35421cf042df5f3ea469ba3e2b0c711edb0e4a17228a2d23175360d1d1f968b0.json

@@ -0,0 +1,12 @@
+{
+  "db_name": "SQLite",
+  "query": "DELETE FROM media_files WHERE owner_kind = 'movie' AND owner_id = ?",
+  "describe": {
+    "columns": [],
+    "parameters": {
+      "Right": 1
+    },
+    "nullable": []
+  },
+  "hash": "35421cf042df5f3ea469ba3e2b0c711edb0e4a17228a2d23175360d1d1f968b0"
+}