Add Forgejo repository health metrics and Grafana dashboard (#245)

## Summary
- New `forgejo_metrics` Ansible role that queries the Forgejo REST API every 60s and writes Prometheus textfile metrics (open PRs, issues, languages, releases, commits, Actions runs/duration/success)
- Grafana dashboard "Forgejo Repository Health" with 12 panels across 4 rows: overview stats, CI/CD health, repository info, and staleness tracking
- Deletes superseded `forgejo-actions-dashboard` plan doc (this implementation covers a broader scope)

## Deployment and Testing
- [ ] `mise run provision-indri -- --tags forgejo_metrics` to deploy the collector
- [ ] `ssh indri 'cat /opt/homebrew/var/node_exporter/textfile/forgejo.prom'` to verify metrics
- [ ] `argocd app sync grafana-config` to deploy the dashboard
- [ ] Check Grafana dashboard "Forgejo Repository Health" loads with data
- [ ] `mise run services-check` passes

Reviewed-on: https://forge.ops.eblu.me/eblume/blumeops/pulls/245

ansible/playbooks/indri.yml

@@ -195,6 +195,23 @@
       no_log: true
       tags: [jellyfin_metrics]
 
+    # Forgejo API token for metrics collection
+    - name: Fetch Forgejo API token for metrics
+      ansible.builtin.command:
+        cmd: op read "op://vg6xf6vvfmoh5hqjjhlhbeoaie/w3663ffnvkewbftncqxtcpeavy/api-token"
+      delegate_to: localhost
+      register: _forgejo_metrics_api_token
+      changed_when: false
+      no_log: true
+      check_mode: false
+      tags: [forgejo_metrics]
+
+    - name: Set Forgejo metrics API token fact
+      ansible.builtin.set_fact:
+        forgejo_metrics_api_key: "{{ _forgejo_metrics_api_token.stdout }}"
+      no_log: true
+      tags: [forgejo_metrics]
+
   roles:
     - role: alloy
       tags: alloy
@@ -218,5 +235,7 @@
       tags: jellyfin
     - role: jellyfin_metrics
       tags: jellyfin_metrics
+    - role: forgejo_metrics
+      tags: forgejo_metrics
     - role: caddy
       tags: caddy