feat: improve model rate limit tracking

apps/api/migrations/0029_rate_limit_reservations.sql

@@ -0,0 +1,23 @@
+CREATE TABLE IF NOT EXISTS gateway_rate_limit_reservations (
+  id uuid PRIMARY KEY DEFAULT gen_random_uuid(),
+  task_id uuid NOT NULL REFERENCES gateway_tasks(id) ON DELETE CASCADE,
+  attempt_id uuid REFERENCES gateway_task_attempts(id) ON DELETE SET NULL,
+  scope_type text NOT NULL,
+  scope_key text NOT NULL,
+  metric text NOT NULL,
+  window_start timestamptz NOT NULL,
+  limit_value numeric NOT NULL,
+  reserved_amount numeric NOT NULL DEFAULT 0,
+  actual_amount numeric NOT NULL DEFAULT 0,
+  status text NOT NULL DEFAULT 'reserved',
+  reason text,
+  created_at timestamptz NOT NULL DEFAULT now(),
+  updated_at timestamptz NOT NULL DEFAULT now(),
+  finalized_at timestamptz
+);
+
+CREATE INDEX IF NOT EXISTS idx_rate_limit_reservations_active
+  ON gateway_rate_limit_reservations(status, scope_type, scope_key, metric, window_start);
+
+CREATE INDEX IF NOT EXISTS idx_rate_limit_reservations_task
+  ON gateway_rate_limit_reservations(task_id, attempt_id);

apps/api/migrations/0030_platform_model_cooldown.sql

@@ -0,0 +1,5 @@
+ALTER TABLE IF EXISTS platform_models
+  ADD COLUMN IF NOT EXISTS cooldown_until timestamptz;
+
+CREATE INDEX IF NOT EXISTS idx_platform_models_cooldown
+  ON platform_models(cooldown_until);