fix(search): pin Ollama model in memory + raise read timeout

NL search recovered after deploy but went 503 again after a few minutes:
Ollama unloads the model after its default ~5 min keep-alive, so the next
query cold-loads the 4.7 GB model and exceeds the backend's 30s read
timeout (ResourceAccessException -> SMART_SEARCH_UNAVAILABLE). Warm
inference is ~18s; the cold load after idle is what timed out.

- docker-compose.{prod,yml}: set OLLAMA_KEEP_ALIVE=-1 on the ollama
  service so the model stays resident and never pays a cold-load penalty
  during normal operation (verified on staging: `ollama ps` -> UNTIL
  "Forever"; host has 47 GB free).
- application.yaml: raise app.ollama.timeout-seconds 30 -> 60 so the one
  unavoidable cold load (first query after an Ollama restart, before the
  model is pinned) completes instead of timing out.

Refs #758

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docker-compose.prod.yml

@@ -239,6 +239,11 @@ services:
       - archiv-net
     volumes:
       - ollama-models:/root/.ollama
+    environment:
+      # Pin the model in memory (no idle unload). Without this, Ollama evicts
+      # the model after ~5 min idle and the next query pays a cold-load penalty
+      # that exceeds the backend read timeout → NL search 503 after idle.
+      OLLAMA_KEEP_ALIVE: "-1"
     cpus: "${OLLAMA_CPU_LIMIT:-4.0}"
     mem_limit: "${OLLAMA_MEM_LIMIT:-8g}"
     memswap_limit: "${OLLAMA_MEM_LIMIT:-8g}"