feat: rampart-tui — live metrics terminal dashboard

- ratatui + crossterm; separate bin reading Prometheus exposition format
- counter table (xdp stats, auto-bans, intel), pps/drops history chart,
  status panel with error banner, q/quit r/refresh
- prometheus text parser (labels, escapes, NaN/Inf), Fetcher trait for tests
- 152 tests green

Cargo.toml

@@ -62,6 +62,10 @@ rand = { version = "0.8", default-features = false, features = ["std", "std_rng"
 clap = { version = "4", features = ["derive"] }
 chrono = { version = "0.4", features = ["serde"] }
 
+# TUI (rampart-tui): лёгкие deps, без feature-gate
+ratatui = "0.30"
+crossterm = "0.29"
+
 axum = "0.8"
 tower-http = { version = "0.6", features = ["cors"] }
 jsonwebtoken = "9"