feat(store): persist poll lane state

backend/internal/store/migrations/0013_poll_passes.sql

@@ -0,0 +1,16 @@
+-- Append-only Lane Pass log. Timestamps are unix milliseconds from the poller's clock.
+CREATE TABLE poll_passes (
+  site        text NOT NULL,
+  ran_at      bigint NOT NULL,
+  skip        text NOT NULL,
+  due         integer NOT NULL,
+  checked     integer NOT NULL,
+  gap_ms      bigint NOT NULL,
+  clamped     boolean NOT NULL,
+  refused     integer NOT NULL,
+  unreachable integer NOT NULL,
+  no_chapter  integer NOT NULL,
+  unfetchable integer NOT NULL,
+  errors      integer NOT NULL,
+  PRIMARY KEY (site, ran_at)
+);