docs(backend): remove legacy monitoring poller endpoints from README

The legacy SSH-scraping MonitoringPoller and its endpoints were
decommissioned earlier; update the backend README endpoint list and
Monitoring description to match the current Alertmanager + Prometheus
targets + Grafana observability model.

backend/README.md

@@ -99,7 +99,7 @@ Or with PYTHONPATH if not installed:
 PYTHONPATH=src uvicorn media_library_viewer_api.main:app --reload --port 8000
 ```
 
-API docs available at: http://localhost:8000/docs
+API docs available at: <http://localhost:8000/docs>
 
 ## Docker
 
@@ -123,7 +123,7 @@ export VITE_OIDC_POST_LOGOUT_REDIRECT_URI=https://manage.example.com/
 docker compose up --build
 ```
 
-2. After the API is running, open the app, go to **Settings**, and add machine entries:
+1. After the API is running, open the app, go to **Settings**, and add machine entries:
    - **Local**: monitors the API host itself without SSH.
    - **SSH**: monitors another machine using a host, username, and a private key pasted directly into the machine settings, with an optional passphrase.
    - The machine editor groups Connection, Monitoring / Files, Jellyfin, Jellyseerr, and Notes under separate headings so each service area is easier to scan.
@@ -132,7 +132,7 @@ docker compose up --build
    - Use **Validate SSH + trust host** in the machine editor before saving if you want to test the banner/auth flow explicitly.
    - The first successful SSH connection uses trust-on-first-use: the backend records that machine's host key into its managed `known_hosts` file automatically, then continues verifying it strictly on later connects.
 
-3. Open **Monitoring** to see one section per configured machine. Each section uses its own collector state, disk path, metrics queries, and recent action history, which are populated automatically by the backend poller.
+2. Open **Monitoring** to see Alertmanager alerts, Prometheus scrape targets, and Grafana deep-links for configured machines. System metrics (disk, CPU, memory) are owned by the external observability stack (Prometheus + node_exporter + Grafana), not by the Manage backend.
 
 For local development, `docker compose -f docker-compose.dev.yml up --build` does not require an SSH key unless you configure remote SSH machines in the Settings tab.
 
@@ -142,14 +142,10 @@ For local development, `docker compose -f docker-compose.dev.yml up --build` doe
 - `GET /api/dashboard/libraries` — Per-library breakdown
 - `GET /api/dashboard/now-playing` — Active playback sessions
 - `GET /api/monitoring/machines` — Persistent monitoring machine definitions
-- `GET /api/monitoring/status?machine_id=` — Collector status for a machine
-- `GET /api/monitoring/metrics?machine_id=` — Resource samples (last hour)
-- `GET /api/monitoring/disk?machine_id=` — Disk space
-- `POST /api/monitoring/start|stop|restart?machine_id=` — Collector controls
-- `GET /api/monitoring/diagnostics?machine_id=` — Collector debug info
-- `GET /api/monitoring/poller` — Backend poller status and configuration
-- `GET /api/monitoring/machines/{machine_id}/actions` — Recent machine action history
-- `GET /api/dashboard/monitoring` — Dashboard-wide per-machine monitoring summary table with 10-minute averages and min/max subtext
+- `GET /api/monitoring/prometheus-targets` — Prometheus file-SD targets for remote Node Exporters
+- `GET /api/monitoring/alerts` — Active Alertmanager alerts summary
+- `GET /api/monitoring/alertmanager-status` — Alertmanager cluster/status
+- `POST /api/monitoring/alertmanager-webhook` — Receive/forward Alertmanager webhooks
 - `GET /api/settings/machines` — Manage machine definitions
 - `GET /api/media/status` — Index status
 - `POST /api/media/build` — Rebuild index