migrations: more database migrations for various database fixes

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: I8567eec6980b2b5453687bcbd07a61206a6a6964

migrations/sqlite/V9__fix_indexes_and_constraints.sql

@@ -0,0 +1,18 @@
+-- Drop redundant indexes (already covered by UNIQUE constraints)
+DROP INDEX IF EXISTS idx_users_username;
+DROP INDEX IF EXISTS idx_user_libraries_user_id;
+
+-- Add missing indexes for comments table
+CREATE INDEX IF NOT EXISTS idx_comments_media ON comments(media_id);
+CREATE INDEX IF NOT EXISTS idx_comments_parent ON comments(parent_comment_id);
+
+-- Remove duplicates before adding unique index (keep the first row)
+DELETE FROM external_metadata
+WHERE rowid NOT IN (
+    SELECT MIN(rowid)
+    FROM external_metadata
+    GROUP BY media_id, source
+);
+
+-- Add unique index for external_metadata to prevent duplicates
+CREATE UNIQUE INDEX IF NOT EXISTS uq_external_metadata_source ON external_metadata(media_id, source);