feat(gateway): TLS auto + rate limit + IP allowlist su write endpoint

Configura il gateway Caddy per il deploy su cerbero-mcp.tielogic.xyz:

- Build custom Caddy con plugin mholt/caddy-ratelimit (Dockerfile +
  build via xcaddy).
- TLS automatico via Let's Encrypt (richiede DNS A record + porte
  80/443 raggiungibili), HSTS preload, header di sicurezza.
- Rate limit per IP (60 req/min sui read, 10 req/min sui write,
  sliding window).
- Allowlist IP sui write endpoint (place_*, cancel_*, set_*, close_*,
  transfer_*, amend_*, switch_*): IP non in WRITE_ALLOWLIST → 403.
- Default WRITE_ALLOWLIST copre loopback + Docker bridge: bot sulla
  stessa macchina (host o container) funziona senza configurazione,
  IP pubblici esterni vanno aggiunti esplicitamente.
- Smoke test e README aggiornati per il nuovo URL gateway.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

gateway/Caddyfile

@@ -1,23 +1,66 @@
 {
 	admin off
-	auto_https off
+	email {$ACME_EMAIL:adrianodalpastro@tielogic.com}
+
+	# Plugin mholt/caddy-ratelimit
+	order rate_limit before basicauth
 }
 
-:8080 {
+cerbero-mcp.tielogic.xyz {
 	log {
 		output stdout
-		format console
+		format json
 	}
 
+	# ───── Security headers ─────
+	header {
+		Strict-Transport-Security "max-age=31536000; includeSubDomains; preload"
+		X-Content-Type-Options "nosniff"
+		X-Frame-Options "DENY"
+		Referrer-Policy "no-referrer"
+		-Server
+	}
+
+	# ───── IP allowlist su endpoint write ─────
+	# WRITE_ALLOWLIST: CIDR space-separated (es. "1.2.3.4/32 5.6.7.0/24").
+	# Default 127.0.0.1/32 — fail-closed se non configurato.
+	@writes_blocked {
+		path_regexp ^/mcp-[a-z]+/tools/(place_|cancel_|set_|close_|transfer_|amend_|switch_)
+		not remote_ip {$WRITE_ALLOWLIST:127.0.0.1/32 ::1/128 172.16.0.0/12}
+	}
+	respond @writes_blocked "forbidden: source ip not in allowlist" 403
+
+	# ───── Rate limit ─────
+	# Reads: 60 req/min/IP, writes: 10 req/min/IP (sliding window).
+	rate_limit {
+		zone reads {
+			match {
+				not path_regexp ^/mcp-[a-z]+/tools/(place_|cancel_|set_|close_|transfer_|amend_|switch_)
+			}
+			key {remote_ip}
+			events 60
+			window 1m
+		}
+		zone writes {
+			match {
+				path_regexp ^/mcp-[a-z]+/tools/(place_|cancel_|set_|close_|transfer_|amend_|switch_)
+			}
+			key {remote_ip}
+			events 10
+			window 1m
+		}
+	}
+
+	# ───── Reverse proxy ─────
 	handle_path /mcp-deribit/* {
 		reverse_proxy mcp-deribit:9011
 	}
-	handle_path /mcp-hyperliquid/* {
-		reverse_proxy mcp-hyperliquid:9012
-	}
 	handle_path /mcp-bybit/* {
 		reverse_proxy mcp-bybit:9019
 	}
+	handle_path /mcp-hyperliquid/* {
+		reverse_proxy mcp-hyperliquid:9012
+	}
 	handle_path /mcp-alpaca/* {
 		reverse_proxy mcp-alpaca:9020
 	}