Add Fly.io public reverse proxy for docs.eblu.me (#120)

## Summary

- Adds a Fly.io reverse proxy (`blumeops-proxy`) that tunnels public traffic to homelab services over Tailscale
- First service exposed: `docs.eblu.me` — the Quartz static docs site
- Includes Pulumi IaC for Tailscale auth key/ACLs and Gandi DNS CNAME
- Adds mise tasks (`fly-deploy`, `fly-setup`, `fly-shutoff`) and Forgejo CI workflow

## Key details

- Fly.io Firecracker VMs support TUN devices natively — no userspace networking needed
- Tailscale auth key is `preauthorized=True` to avoid device approval hangs on container restarts
- nginx caches aggressively for the static site; health check is on the default_server block
- ACLs restrict `tag:flyio-proxy` to `tag:k8s` on port 443 only
- DNS CNAME deployed and verified: `docs.eblu.me` → `blumeops-proxy.fly.dev`

## Test plan

- [x] `curl -sf https://blumeops-proxy.fly.dev/healthz` returns `ok`
- [x] `curl -I -H "Host: docs.eblu.me" https://blumeops-proxy.fly.dev/` returns 200 with `X-Cache-Status`
- [x] `curl -I https://docs.eblu.me/` returns 200 with valid Let's Encrypt cert
- [x] `dig forge.ops.eblu.me` still resolves to 100.98.163.89 (private services unaffected)
- [x] Set `FLY_DEPLOY_TOKEN` Forgejo Actions secret for CI auto-deploy

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Reviewed-on: https://forge.ops.eblu.me/eblume/blumeops/pulls/120

.forgejo/workflows/deploy-fly.yaml

@@ -0,0 +1,37 @@
+name: Deploy Fly.io Proxy
+
+on:
+  workflow_dispatch:
+  push:
+    branches: [main]
+    paths:
+      - 'fly/**'
+
+jobs:
+  deploy:
+    runs-on: k8s
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Install flyctl
+        run: |
+          curl -L https://fly.io/install.sh | sh
+          echo "/root/.fly/bin" >> "$GITHUB_PATH"
+
+      - name: Deploy to Fly.io
+        env:
+          FLY_API_TOKEN: ${{ secrets.FLY_DEPLOY_TOKEN }}
+        run: |
+          cd fly
+          fly deploy
+
+      - name: Verify health
+        env:
+          FLY_API_TOKEN: ${{ secrets.FLY_DEPLOY_TOKEN }}
+        run: |
+          fly status -a blumeops-proxy
+          echo ""
+          echo "Health check:"
+          sleep 10
+          curl -sf https://blumeops-proxy.fly.dev/healthz || echo "Warning: health check failed (may need DNS propagation)"