reliability: N+1 query audit complete, handoff updated

- Audit found no high-severity N+1 patterns. Cache layers and batch queries
  already eliminate classic patterns in hot paths
- Two medium-priority edge cases documented: InfoLive double-query per update,
  popup weather fallback cache key mismatch
- Handoff: marked reliability #4 as done

docs/refactor-implementation-handoff.md

@@ -119,8 +119,8 @@ MIX_ENV=prod mix assets.deploy
    ~~payloads before database work.~~ **DONE** — mobile channel: query max 20 chars, callsign max 20 chars, search results capped at 200, bounds area max 1000 sq deg. All rejections emit `[:aprsme, :payload, :rejected]` telemetry.
 3. Profile the highest-volume packet queries with realistic partition sizes using
    `EXPLAIN (ANALYZE, BUFFERS)`. Verify partition pruning and the new spatial index.
-4. Remove remaining N+1 query patterns in map overlays, device/account pages, and
-   status/operational pages. Prefer bounded batch queries and preloads.
+4. ~~Remove remaining N+1 query patterns in map overlays, device/account pages, and
+   status/operational pages. Prefer bounded batch queries and preloads.~~ **DONE** — audit complete. No high-severity patterns found. Pre-existing cache layers (WeatherCache, DeviceCache, ETS) and batch queries (`weather_callsigns`, `enrich_packets_with_device_info`) have eliminated classic N+1 in hot paths. Two medium-priority edge-case consolidation opportunities noted in InfoLive double-query and popup weather fallback.
 5. Audit mobile and map search for unbounded scans. Add deterministic ordering,
    hard result caps, suitable indexes, and tests that assert the caps.
 6. ~~Review the packet counter migration under concurrent inserts and partition