docs(infra): correct server specs — Hetzner Serverbörse i7-6700 64 GB, not CX32

Replace all references to the CX32 VPS (8 GB RAM, Hetzner Cloud) with the
actual production server: a Hetzner Serverbörse dedicated server with an
Intel Core i7-6700 (4C/8T, 3.4 GHz) and 64 GB RAM.

Affected files:
- .claude/personas/devops.md — monthly cost line + upgrade example
- docs/infrastructure/production-compose.md — sizing section + cost table
- docs/DEPLOYMENT.md — OCR memory table + OCR_MEM_LIMIT env var description
- docs/adr/004-pdfbox-thumbnails.md — thumbnailExecutor memory ceiling note
- docs/adr/021-tmpdir-persistent-volume-staging.md — OOMKill rationale in alternatives

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

docs/infrastructure/production-compose.md

@@ -20,24 +20,19 @@ The observability stack (Prometheus, Loki, Grafana, Tempo, GlitchTip) ships as a
 
 ---
 
-## VPS Sizing Recommendations
+## Server Sizing
 
-### Recommended: Hetzner CX32
+### Current Production Server: Hetzner Dedicated (Serverbörse)
 
-**Specs**: 4 vCPU, 8 GB RAM, 80 GB SSD · **Cost**: 17 EUR/mo
+**Specs**: Intel Core i7-6700 (4C/8T, 3.4 GHz), 64 GB RAM · acquired via Hetzner server auction
 
-Sufficient for the application stack (Postgres, MinIO, OCR with `mem_limit: 12g`, backend, frontend, Caddy) on a CX32 today. Once the observability stack lands (Prometheus/Loki/Grafana/Alertmanager add ~2 GB) consider a CX42.
+Comfortably handles the full application stack (Postgres, MinIO, OCR with `mem_limit: 12g`, backend, frontend, Caddy, full observability stack) with headroom to spare. The 64 GB RAM means OCR, Ollama inference, and the observability stack can all run concurrently without memory pressure.
 
-### When to Upgrade: Hetzner CX42
+### When to Reconsider Hardware
 
-**Specs**: 8 vCPU, 16 GB RAM · **Cost**: 29 EUR/mo
-
-Upgrade when:
-- Observability stack adds memory pressure (Loki + Grafana with >30 days retention)
-- OCR throughput needs scaling beyond a single-node Surya/Kraken setup
-- Real user load profiled in Grafana shows response-time degradation
-
-Never upgrade the VPS tier before profiling — most perceived performance issues are application bugs, not resource constraints.
+- CPU is Skylake (2015) — single-threaded performance is the likely bottleneck before RAM
+- Profile with Grafana dashboards before concluding hardware is the constraint
+- Most perceived performance issues are application bugs (unindexed queries, N+1 loads), not resource limits
 
 ---
 
@@ -45,12 +40,11 @@ Never upgrade the VPS tier before profiling — most perceived performance issue
 
 | Service | Cost |
 |---|---|
-| Hetzner CX32 VPS | 17.00 EUR |
+| Hetzner dedicated server (Serverbörse, i7-6700, 64 GB RAM) | see invoice |
 | Hetzner DNS | 0.00 EUR |
 | Hetzner SMTP relay | ~1.00 EUR |
-| **Total** | **~18 EUR/mo** |
 
-MinIO data lives on the VPS disk (no Object Storage line item yet). The Hetzner OBS migration would add ~5 EUR/mo at ~200 GB.
+MinIO data lives on the server disk (no Object Storage line item yet). The Hetzner OBS migration would add ~5 EUR/mo at ~200 GB.
 
 Equivalent SaaS stack: 200–300 EUR/mo.