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

fly/start.sh

@@ -0,0 +1,17 @@
+#!/bin/sh
+set -e
+
+# Start tailscale daemon. Fly.io runs Firecracker microVMs which support
+# TUN devices natively — no need for --tun=userspace-networking.
+tailscaled --statedir=/var/lib/tailscale &
+sleep 2
+
+# Authenticate and join tailnet
+tailscale up --authkey="${TS_AUTHKEY}" --hostname=flyio-proxy
+
+# Wait for tailscale to be ready
+until tailscale status > /dev/null 2>&1; do sleep 1; done
+echo "Tailscale connected"
+
+# Start nginx — MagicDNS resolves *.tail8d86e.ts.net hostnames
+nginx -g "daemon off;"