docs: update README quick-start with Prometheus/Grafana and Docker publish

README.md

@@ -18,9 +18,10 @@ publisher (OBS / FFmpeg / SRT) ──▶  datarhei Core  ──▶  WebRTC peers
 Sub-second glass-to-glass on a LAN over WHEP, no SFU dependencies,
 single binary, single Docker image.
 
-> **Status:** v0.2.0-dragonfork shipped 2026-05-03. Full GUI bundled
-> (Restreamer UI + Wild Dragon WebRTC admin). Live deploy running on
-> TrueNAS since 2026-04-17.
+> **Status:** v0.2 in progress (last work 2026-05-06). Full GUI bundled
+> (Restreamer UI + Wild Dragon WebRTC admin). Prometheus + Grafana
+> observability stack shipped. Live deploy running on TrueNAS since
+> 2026-04-17.
 
 ## What this fork adds
 
@@ -41,6 +42,9 @@ single binary, single Docker image.
 - **Browser-side smoke player** at `whep-player.html` — zero-dependency
   WHEP subscriber, ICE/codec/bitrate stats, JWT field, shareable
   `?url=&token=` URLs.
+- **Prometheus observability** — eleven `dragonfork_webrtc_*` metrics
+  (RED-method counters/histograms + state gauges). Grafana health
+  dashboard with 5 rows and 4 pre-loaded alert rules.
 - **Multi-viewer correctness:** per-stream peer cap, ICE-failure
   auto-cleanup, process-stop broadcast tear-down.
 - **Error matrix** per the design spec: `406` on codec mismatch,
@@ -64,6 +68,9 @@ CORE_HTTP_PORT=8080
 API_AUTH_USERNAME=admin
 API_AUTH_PASSWORD=$(openssl rand -base64 24)
 API_AUTH_JWT_SECRET=$(openssl rand -base64 48)
+GRAFANA_ADMIN_PASSWORD=$(openssl rand -base64 24)
+GRAFANA_PORT=3000
+PROM_PORT=9090
 EOF
 
 docker compose up -d --build
@@ -76,11 +83,21 @@ Then open in a browser (replace `<host>` with your `PUBLIC_IP`):
 | `http://<host>:8080/` | **Restreamer UI** — manage processes, ingests, outputs |
 | `http://<host>:8080/wilddragon-webrtc.html` | **Wild Dragon WebRTC admin** — toggle `webrtc.enabled` per process, copy WHEP URL |
 | `http://<host>:8080/whep-player.html` | **WHEP smoke player** — verify the WebRTC stream renders |
+| `http://<host>:3000/` | **Grafana** — WebRTC Health dashboard (login with `GRAFANA_ADMIN_PASSWORD`) |
+| `http://<host>:9090/` | **Prometheus** — raw metrics, alert rules |
 | `http://<host>:8080/api/swagger/index.html` | **Swagger** — full API docs |
 
 The Restreamer UI doesn't yet have a WebRTC checkbox in its process
 editor — use `/wilddragon-webrtc.html` for that. Tracked in issue #15.
 
+### Pulling a pre-built image (after first tag is published)
+
+```sh
+# Update .env, then:
+docker compose pull   # pulls pre-built multi-arch image
+docker compose up -d  # no --build needed
+```
+
 ### Sample process JSON
 
 ```json
@@ -119,7 +136,8 @@ SDI + file audio), use the `video_map` and `audio_map` fields:
 | Design spec | [`docs/design/2026-04-16-datarhei-dragon-fork-webrtc-design.md`](docs/design/2026-04-16-datarhei-dragon-fork-webrtc-design.md) |
 | M1 (PoC) plan | [`docs/design/2026-04-16-datarhei-dragon-fork-m1-webrtc-poc.md`](docs/design/2026-04-16-datarhei-dragon-fork-m1-webrtc-poc.md) |
 | M2 (Core integration) spec | [`docs/design/2026-04-17-datarhei-dragon-fork-m2-webrtc-core-integration.md`](docs/design/2026-04-17-datarhei-dragon-fork-m2-webrtc-core-integration.md) |
-| Prometheus metrics design (deferred) | [`docs/design/2026-05-03-datarhei-dragon-fork-webrtc-prometheus-metrics-design.md`](docs/design/2026-05-03-datarhei-dragon-fork-webrtc-prometheus-metrics-design.md) |
+| Prometheus metrics design | [`docs/design/2026-05-03-datarhei-dragon-fork-webrtc-prometheus-metrics-design.md`](docs/design/2026-05-03-datarhei-dragon-fork-webrtc-prometheus-metrics-design.md) |
+| Upstream rebase policy | [`docs/REBASE.md`](docs/REBASE.md) |
 | TrueNAS deploy guide | [`deploy/truenas/core/README.md`](deploy/truenas/core/README.md) |
 | Testing | [`test/TESTING.md`](test/TESTING.md) |
 | Changelog (Dragon Fork) | [`CHANGELOG.md`](CHANGELOG.md) |
@@ -136,6 +154,21 @@ go test -tags latency -timeout 90s -count=1 \
   -run TestLatencyServerHop ./app/webrtc/...   # latency p95 gate
 ```
 
+## Load testing
+
+```sh
+go run ./test/load/sustained.go \
+  -url http://<host>:8080 \
+  -stream <processID> \
+  -peers 5 \
+  -duration 10m \
+  -auth "Bearer <TOKEN>" \
+  -out test/load/results/
+```
+
+Reports are written to `test/load/results/`. Observe the Grafana
+WebRTC Health dashboard during the run.
+
 ## From upstream Datarhei
 
 This fork preserves everything upstream Datarhei Core does — Dragon