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>

src/question.rs

@@ -33,6 +33,33 @@ impl QueryType {
             _ => QueryType::UNKNOWN(num),
         }
     }
+
+    pub fn as_str(&self) -> &'static str {
+        match self {
+            QueryType::A => "A",
+            QueryType::NS => "NS",
+            QueryType::CNAME => "CNAME",
+            QueryType::MX => "MX",
+            QueryType::AAAA => "AAAA",
+            QueryType::UNKNOWN(_) => "UNKNOWN",
+        }
+    }
+
+    pub fn parse_str(s: &str) -> Option<QueryType> {
+        if s.eq_ignore_ascii_case("A") {
+            Some(QueryType::A)
+        } else if s.eq_ignore_ascii_case("NS") {
+            Some(QueryType::NS)
+        } else if s.eq_ignore_ascii_case("CNAME") {
+            Some(QueryType::CNAME)
+        } else if s.eq_ignore_ascii_case("MX") {
+            Some(QueryType::MX)
+        } else if s.eq_ignore_ascii_case("AAAA") {
+            Some(QueryType::AAAA)
+        } else {
+            None
+        }
+    }
 }
 
 #[derive(Debug, Clone, PartialEq, Eq)]