Implement WP-0011 hub service, CLI, and deployment artifacts

Add FederationHubAPI spec, hub registration schema, FastAPI hub with SQLite
persistence, reuse-surface hub CLI client, Dockerfile, and hub tests. Activate
workplan; T05 deploy and T06 ops docs remain open pending railiance01 cutover.

docs/deploy/hub-kubernetes.md

@@ -0,0 +1,32 @@
+# Federation Hub — Kubernetes Deployment
+
+Companion to **RAILIANCE-WP-0007** (`railiance-apps` Helm release).
+
+## Image
+
+```bash
+docker build -t gitea.coulomb.social/coulomb/reuse-surface-hub:<tag> .
+docker push gitea.coulomb.social/coulomb/reuse-surface-hub:<tag>
+```
+
+## Required environment
+
+| Variable | Purpose |
+|---|---|
+| `REUSE_SURFACE_HUB_TOKEN` | Bearer token for write API |
+| `REUSE_SURFACE_HUB_DB` | SQLite path (default `/data/hub.db`) |
+| `REUSE_SURFACE_HUB_CACHE_DIR` | Remote index cache (default `/data/cache`) |
+
+Mount a PVC at `/data` for persistence.
+
+## Probes
+
+- Liveness/readiness: `GET /health` on port `8000`
+
+## Client configuration
+
+```bash
+export REUSE_SURFACE_HUB_URL=https://reuse-hub.whywhynot.de
+export REUSE_SURFACE_HUB_TOKEN=<write-token>
+reuse-surface hub status
+```