docs(ollama): add model upgrade runbook + post-deploy smoke test to DEPLOYMENT.md

Addresses Elicit's and Sara's review concerns on PR #749:
- Expand §6 ollama_models section into a full model upgrade runbook (step-by-step
  docker volume rm + recreate, including production volume name prefix)
- Add re-deploy idempotency note to §3.4 (init container exits quickly when model
  already present on the volume)
- Add NL search smoke test to §3.4 (curl command distinguishing 200 from 503
  NL_SEARCH_UNAVAILABLE)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/DEPLOYMENT.md

@@ -280,6 +280,15 @@ git.raddatz.cloud      A   <server IP>
 > **First start — Ollama model pull:** On first `docker compose up -d`, the `ollama-model-init` container pulls `qwen2.5:7b-instruct-q4_K_M` (~4.7 GB). At 10 Mbps this takes approximately 60–90 minutes; at 100 Mbps approximately 6–10 minutes. The pull is a one-time operation — subsequent restarts skip it (model already on the `ollama_models` volume). Monitor progress with `docker logs -f $(docker ps -q --filter name=ollama-model-init)`.
 >
 > **Do not use `--wait` on first deploy** — `docker compose up -d --wait` waits for all services to reach their health/completion target, including `ollama-model-init`. On first pull this blocks for 60–90 minutes and will time out any CI/deploy script that uses `--wait`.
+>
+> **Re-deploy idempotency:** on subsequent `docker compose up -d` runs (including `--force-recreate`), `ollama-model-init` re-executes but exits in seconds — Ollama's CLI skips the download when the model digest already matches what is on the volume.
+>
+> **Verify NL search is active** after enabling Ollama (`APP_OLLAMA_BASE_URL=http://ollama:11434`):
+> ```bash
+> curl -s http://localhost:8080/api/nl-search?q=brief+von+grossmutter
+> # Returns 200 with results → NL search is active
+> # Returns 503 NL_SEARCH_UNAVAILABLE → Ollama is not reachable or APP_OLLAMA_BASE_URL is unset
+> ```
 
 ```bash
 # 1. Trigger nightly.yml manually (Repo → Actions → nightly → "Run workflow")
@@ -576,13 +585,23 @@ bash scripts/download-kraken-models.sh
 
 > Downloads the Kurrent/Sütterlin HTR models. Run once after a fresh clone or when models are updated.
 
-### Manage the `ollama_models` volume
+### Upgrade the Ollama model
 
-> **`ollama_models` volume:** holds model weights only — fully reproducible by re-pull, no backup needed. If the volume fills after a model upgrade:
-> ```bash
-> docker volume rm ollama_models && docker compose up -d
-> ```
-> The init container re-pulls the model on next startup.
+To switch to a newer model version (e.g. a future release of `qwen2.5`):
+
+1. Update the model name in the `ollama-model-init` `command:` in `docker-compose.yml`.
+2. Remove the existing model volume to free the old weights:
+   ```bash
+   docker volume rm familienarchiv_ollama_models
+   ```
+   (In production the volume name is prefixed with the compose project: `archiv-production_ollama_models`.)
+3. Restart the stack:
+   ```bash
+   docker compose up -d
+   ```
+   The `ollama-model-init` container pulls the new model weights on first start (~4–8 GB download depending on the model). The `ollama` inference server will not start until the pull completes (`condition: service_completed_successfully`).
+
+> **`ollama_models` volume:** holds model weights only — fully reproducible by re-pull, no backup needed.
 
 ### Trigger a canonical import