server: add indexes that should help with bulk read

server/migrations/20260108161023_add_year_index_to_movie_sets.down.sql

@@ -0,0 +1,2 @@
+DROP INDEX IF EXISTS movie_sets_year_id_idx;
+DROP INDEX IF EXISTS movie_sets_year_idx;

server/migrations/20260108161023_add_year_index_to_movie_sets.up.sql

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+-- Add index on movie_sets.year to speed up year-based queries
+CREATE INDEX movie_sets_year_idx ON movie_sets(year);
+
+-- Composite index for queries that filter by year and return id
+-- This can make the subquery in UPDATE statements even faster
+CREATE INDEX movie_sets_year_id_idx ON movie_sets(year, id);