add ad blocking, live dashboard, system DNS auto-discovery

- DNS-level ad blocking: 385K+ domains via Hagezi Pro blocklist, subdomain
  matching, one-click allowlist, pause/toggle, background refresh every 24h
- Live dashboard at :5380 with real-time stats, query log, override
  management (create/edit/delete), blocking controls
- System DNS auto-discovery: parses scutil --dns on macOS to find
  conditional forwarding rules (Tailscale, VPN split-DNS)
- REST API expanded to 18 endpoints (blocking, overrides, diagnostics)
- Startup banner with colored system info
- Performance benchmarks (bench/dns-bench.sh)
- Landing page updated with new positioning and comparison table
- CI, Dockerfile, LICENSE, development plan docs

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

LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 Razvan Dimescu
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.