fix(db): renumber colliding 0011 migration to 0012

PRs #97 and #98 each added a migration numbered 0011; merged together
sqlx hits UNIQUE on _sqlx_migrations.version.

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

crates/arr-db/migrations/0012_vanished_grabs.sql

@@ -0,0 +1,25 @@
+-- #86: a grab whose torrent Transmission no longer reports (manual removal,
+-- not a policy failure) gets its own state. Distinct from 'failed' so it
+-- does not feed the needs_decision attention queue (attention.rs), which
+-- counts 'failed' as a hard-fail signal. SQLite cannot alter a CHECK, so the
+-- table is rebuilt (see 0010).
+CREATE TABLE grabs_new (
+    id          INTEGER PRIMARY KEY,
+    release_id  INTEGER NOT NULL REFERENCES releases (id),
+    target_kind TEXT NOT NULL CHECK (target_kind IN ('movie', 'episode', 'season')),
+    target_id   INTEGER NOT NULL,
+    infohash    TEXT NOT NULL UNIQUE,
+    state       TEXT NOT NULL DEFAULT 'sent'
+                CHECK (state IN ('sent', 'downloaded', 'imported', 'failed', 'vanished')),
+    grabbed_at  TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ', 'now')),
+    imported_at TEXT
+) STRICT;
+
+INSERT INTO grabs_new (id, release_id, target_kind, target_id, infohash, state, grabbed_at, imported_at)
+SELECT id, release_id, target_kind, target_id, infohash, state, grabbed_at, imported_at FROM grabs;
+
+DROP TABLE grabs;
+ALTER TABLE grabs_new RENAME TO grabs;
+
+CREATE INDEX grabs_state ON grabs (state);
+CREATE INDEX grabs_target ON grabs (target_kind, target_id);