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-bd10698fda9b55789f3b5806cda9ccaf45973fbe052f5ef4fdf693529e24f994.json

@@ -0,0 +1,20 @@
+{
+  "db_name": "SQLite",
+  "query": "SELECT r.path AS \"path!: String\" FROM roots r JOIN movies m ON m.root_id = r.id WHERE m.id = ?",
+  "describe": {
+    "columns": [
+      {
+        "name": "path!: String",
+        "ordinal": 0,
+        "type_info": "Text"
+      }
+    ],
+    "parameters": {
+      "Right": 1
+    },
+    "nullable": [
+      false
+    ]
+  },
+  "hash": "bd10698fda9b55789f3b5806cda9ccaf45973fbe052f5ef4fdf693529e24f994"
+}