Implement XDP firewall with real-time TUI monitoring

Features:
- High-performance packet filtering via eBPF/XDP
- Instant blocklist with dynamic CLI management
- Exact-match rules with Drop/Pass/Log actions
- CIDR-based IP range dropping via LPM trie
- Token-bucket rate limiting (IP-based and flow-based)
- Auto temp bans for rate limit violators
- Real-time event logging via BPF ring buffer
- Interactive TUI monitor with live stats

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

xdp-firewall-common/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "xdp-firewall-common"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+aya = { version = "0.13.1", optional = true }
+
+[features]
+userspace = ["aya"]