fix: BUG-20 clamp trips sequence after recompute + renumber migration

server/sql/migrate_phase29_trip_ids.sql

@@ -0,0 +1,26 @@
+-- Phase 29 (BUG-20): compact trip IDs and stop BIGSERIAL inflation.
+-- trips.id has no foreign-key references (deleted_trip_markers keys on
+-- (device_id, start_time)), so renumbering is purely cosmetic.
+BEGIN;
+
+-- Shift all ids up first so the compact ids (1..N) can't collide with any
+-- id that still exists during the renumber.
+UPDATE trips SET id = id + 1000000;
+
+-- Renumber compactly in start_time order.
+WITH renumbered AS (
+    SELECT id, row_number() OVER (ORDER BY start_time, id) AS new_id
+    FROM trips
+)
+UPDATE trips t
+SET id = r.new_id
+FROM renumbered r
+WHERE t.id = r.id;
+
+-- Reset the sequence to the real max id so the next insert gets MAX(id) + 1.
+SELECT setval(
+    pg_get_serial_sequence('trips', 'id'),
+    (SELECT COALESCE(MAX(id), 0) FROM trips)
+);
+
+COMMIT;