feat(daemon): refresh metadata on add

The metadata lane runs daily, so a series added a moment ago showed no
seasons for up to 24 hours and a movie had no digital release date —
the field §6.2 gates targeted search on.

AppState now carries a MetadataCommand channel alongside the movie,
episode and season ones. Both create handlers send on it after the row
is committed, and a new daemon lane drains it. Its own task rather than
an arm of manual::run: a refresh against TMDB can take a while and must
not sit in front of an operator's manual search.

The add never waits on TMDB and never fails because of it. A refresh
that fails leaves metadata_refreshed_at NULL, which is what the daily
sweep already treats as due, so the title is retried rather than lost.
A command naming a title deleted in between finds no row and does
nothing. METADATA_INTERVAL is unchanged.

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

.sqlx/query-a1be0fa3691226439f768d11600337f18909a58d0f863c794f93f8285b9133c8.json

@@ -0,0 +1,26 @@
+{
+  "db_name": "SQLite",
+  "query": "SELECT tmdb_id AS \"tmdb_id!: i64\", metadata_refreshed_at\n           FROM movies WHERE id = ?",
+  "describe": {
+    "columns": [
+      {
+        "name": "tmdb_id!: i64",
+        "ordinal": 0,
+        "type_info": "Integer"
+      },
+      {
+        "name": "metadata_refreshed_at",
+        "ordinal": 1,
+        "type_info": "Text"
+      }
+    ],
+    "parameters": {
+      "Right": 1
+    },
+    "nullable": [
+      false,
+      true
+    ]
+  },
+  "hash": "a1be0fa3691226439f768d11600337f18909a58d0f863c794f93f8285b9133c8"
+}