wip on autotagging

backend/database/sql/schemas/audio_files.sql

@@ -13,6 +13,11 @@ CREATE TABLE IF NOT EXISTS audio_files (
   library_id int NOT NULL DEFAULT 0,
   play_count int NOT NULL DEFAULT 0,
   last_played datetime,
+  tag_status TEXT NOT NULL DEFAULT 'untagged'
+    CHECK(tag_status IN (
+      'untagged', 'auto_matched', 'user_confirmed', 'user_skipped_permanent'
+    )),
+  group_key TEXT NOT NULL DEFAULT '',
   FOREIGN KEY(file_type_id) REFERENCES file_types(id),
   FOREIGN KEY(recording_id) REFERENCES recordings(id),
   FOREIGN KEY(library_id) REFERENCES libraries(id)
@@ -24,3 +29,11 @@ CREATE INDEX IF NOT EXISTS idx_audio_files_recording_id
 -- idx_audio_files_library_id is created by migration 6 (not here) because
 -- on existing databases this schema file is a no-op (CREATE TABLE IF NOT EXISTS)
 -- and the library_id column doesn't exist until the migration adds it.
+--
+-- idx_audio_files_tag_status_untagged + idx_audio_files_group_key are
+-- created by migrations 31 and 32 for the same reason — on a pre-31
+-- database the partial index predicates (`WHERE tag_status = '...'`
+-- and `WHERE group_key != ''`) would reference columns that don't
+-- yet exist, since CREATE TABLE IF NOT EXISTS does not add columns
+-- to existing tables.  sqlc still sees the columns above, and fresh
+-- DBs pick up the indexes inside the migrations.