feat(analytics): enrich query_logs metadata + query_log_insights view

For continuous optimization we need to attribute slow/failed decodes to
the right cause. query_logs.timings jsonb is now a structured decode-meta
blob, not just stage timings:

- wmi: first 3 chars of VIN (per-brand aggregation)
- result_kind: vehicle / pcat_candidates / emex_candidates / unknown / aborted
- cache_source: db_hit / redis_positive / redis_negative / lock_wait / miss
- candidate_pick: pcat / emex / none (when user picks from candidate modal)
- pcat_car_count, emex_candidate_count (cardinality, drives candidate-modal rate)
- pl24_circuit_open, pl24_skipped (CB state at request time)
- vin_api_used, vin_api timing (NHTSA fallback frequency)

Migration 0003 adds a query_log_insights VIEW that flattens these keys
into typed columns, so ad-hoc SQL doesn't need json operators. New meta
keys appear automatically as NULL; the VIEW stays stable.

docs/analytics-queries.sql has 8 starter queries: cache hit ratio,
per-source latency, slowest WMIs, stage breakdowns, CB/abort frequency,
candidate-modal rate, top failing VINs, dedup effectiveness.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/api/drizzle/0003_query_log_insights.sql

@@ -0,0 +1,32 @@
+-- Analytics-friendly view over query_logs.
+-- Flattens commonly-queried keys from the `timings` jsonb so ad-hoc SQL
+-- doesn't need to remember every json path. New keys can be added without
+-- breaking existing queries (json operator returns NULL for missing keys).
+CREATE OR REPLACE VIEW "query_log_insights" AS
+SELECT
+  ql.id,
+  ql.user_id,
+  ql.vin,
+  substring(ql.vin from 1 for 3) AS wmi,
+  ql.brand_id,
+  ql.source,
+  ql.success,
+  ql.response_time_ms,
+  ql.error_message,
+  ql.created_at,
+  (ql.timings->>'result_kind')                AS result_kind,
+  (ql.timings->>'cache_source')               AS cache_source,
+  (ql.timings->>'candidate_pick')             AS candidate_pick,
+  (ql.timings->>'pcat')::int                  AS pcat_ms,
+  (ql.timings->>'emex')::int                  AS emex_ms,
+  (ql.timings->>'pl24')::int                  AS pl24_ms,
+  (ql.timings->>'vin_api')::int               AS vin_api_ms,
+  (ql.timings->>'lock_wait')::int             AS lock_wait_ms,
+  (ql.timings->>'pcat_car_count')::int        AS pcat_car_count,
+  (ql.timings->>'emex_candidate_count')::int  AS emex_candidate_count,
+  (ql.timings->>'pl24_circuit_open')::bool    AS pl24_circuit_open,
+  (ql.timings ? 'pl24_skipped')               AS pl24_skipped,
+  (ql.timings ? 'aborted')                    AS aborted,
+  (ql.timings->>'vin_api_used')::bool         AS vin_api_used,
+  ql.timings AS raw_meta
+FROM query_logs ql;

apps/api/drizzle/meta/_journal.json

@@ -22,6 +22,13 @@
       "when": 1778584574615,
       "tag": "0002_boring_the_stranger",
       "breakpoints": true
+    },
+    {
+      "idx": 3,
+      "version": "7",
+      "when": 1778587000000,
+      "tag": "0003_query_log_insights",
+      "breakpoints": true
     }
   ]
 }