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

mise-tasks/fly-setup

@@ -0,0 +1,27 @@
+#!/usr/bin/env bash
+#MISE description="One-time setup: configure Fly.io secrets and certs (idempotent)"
+
+set -euo pipefail
+
+APP="blumeops-proxy"
+
+# Fetch Tailscale auth key from Pulumi state
+echo "Fetching Tailscale auth key from Pulumi..."
+TS_AUTHKEY=$(cd "$(dirname "$0")/../pulumi/tailscale" && pulumi stack select tail8d86e && pulumi stack output flyio_authkey --show-secrets)
+fly secrets set TS_AUTHKEY="$TS_AUTHKEY" --stage -a "$APP"
+echo "Tailscale auth key staged (will take effect on next deploy)"
+
+# Allocate IPs (idempotent — fly errors if already allocated)
+# Shared IPv4 is free and sufficient for HTTP/HTTPS services.
+# Use 'fly ips allocate-v4' (no --shared) for dedicated IPv4 ($2/mo)
+# if the service needs non-HTTP protocols.
+fly ips allocate-v4 --shared -a "$APP" 2>/dev/null || true
+fly ips allocate-v6 -a "$APP" 2>/dev/null || true
+echo "IPs allocated"
+
+# Add certs for all public domains (idempotent — fly ignores duplicates)
+fly certs add docs.eblu.me -a "$APP" 2>/dev/null || true
+# fly certs add wiki.eblu.me -a "$APP" 2>/dev/null || true  # future services
+echo "Certificates configured"
+
+echo "Done. Run 'mise run fly-deploy' to deploy."