Optimize slow select queries (#752)

crates/db/migrations/20250917123000_optimize_selects_and_cleanup_indexes.sql

@@ -0,0 +1,21 @@
+PRAGMA foreign_keys = ON;
+
+-- 1) task_attempts: filter by task_id and sort by created_at DESC
+CREATE INDEX IF NOT EXISTS idx_task_attempts_task_id_created_at
+ON task_attempts (task_id, created_at DESC);
+
+-- Global listing ordered by created_at DESC
+CREATE INDEX IF NOT EXISTS idx_task_attempts_created_at
+ON task_attempts (created_at DESC);
+
+-- 2) execution_processes: filter by task_attempt_id and sort by created_at ASC
+CREATE INDEX IF NOT EXISTS idx_execution_processes_task_attempt_created_at
+ON execution_processes (task_attempt_id, created_at ASC);
+
+-- Drop redundant single-column index superseded by the composite above
+DROP INDEX IF EXISTS idx_execution_processes_task_attempt_id;
+
+-- 3) tasks: list by project ordered by created_at DESC
+CREATE INDEX IF NOT EXISTS idx_tasks_project_created_at
+ON tasks (project_id, created_at DESC);
+