Drop canonical_id from tags

libmarlin/src/db/migrations/0001_initial_schema.sql

@@ -17,7 +17,6 @@ CREATE TABLE IF NOT EXISTS tags (
     id           INTEGER PRIMARY KEY,
     name         TEXT    NOT NULL,           -- tag segment
     parent_id    INTEGER REFERENCES tags(id) ON DELETE CASCADE,
-    canonical_id INTEGER REFERENCES tags(id) ON DELETE SET NULL,
     UNIQUE(name, parent_id)
 );
 

libmarlin/src/db/migrations/0006_drop_tags_canonical_id.sql

@@ -0,0 +1,6 @@
+PRAGMA foreign_keys = ON;
+PRAGMA journal_mode = WAL;
+
+-- Remove canonical_id column from tags table
+ALTER TABLE tags DROP COLUMN canonical_id;
+

libmarlin/src/db/mod.rs

@@ -41,6 +41,10 @@ const MIGRATIONS: &[(&str, &str)] = &[
         "0005_add_dirty_table.sql",
         include_str!("migrations/0005_add_dirty_table.sql"),
     ),
+    (
+        "0006_drop_tags_canonical_id.sql",
+        include_str!("migrations/0006_drop_tags_canonical_id.sql"),
+    ),
 ];
 
 /* ─── connection bootstrap ────────────────────────────────────────── */