Refactor architecture: extract reconciler, add interfaces, reduce complexity, improve test coverage

Architecture:
- Extract reconcileNetworking into internal/reconcile package with 7 consumer-side interfaces
- Add locked modifyState helper to fix state.yaml read-modify-write race condition
- Extract CrowdSec and VPN handler groups with interfaces documenting dependency surface
- Replace raw map[string]any YAML manipulation with typed AddDHCPStaticLease/RemoveDHCPStaticLease
- Extract Cloudflare API functions into cfClient struct, eliminating repeated auth boilerplate

Complexity reduction:
- haproxy.GenerateWithOpts: 50 → 6 (extracted 8 focused helpers)
- reconcile.Reconcile: 42 → 11 (extracted buildRoutes, buildDNSEntries, writeHAProxyConfig)
- AutheliaUpdateConfig: 25 → 10 (extracted enableAuthelia/disableAuthelia)

Test coverage improvements:
- reconcile: 4.5% → 56.8% (stub-based tests for route building, DNS entries, orchestration)
- dnsfilter: 10.7% → 45.6% (Manager.Compile, AddList, ToggleList, custom entries)
- config: 67.3% → 89.8% (DHCP static lease mutation tests)

internal/config/extraports_test.go

@@ -100,7 +100,7 @@ func TestExtraPortsYAML_StructuredRoundTrip(t *testing.T) {
 func TestSplitExtraPorts(t *testing.T) {
 	ports := []ExtraPort{
 		{Port: 22, Protocol: "tcp"},
-		{Port: 80},              // default = tcp
+		{Port: 80}, // default = tcp
 		{Port: 5353, Protocol: "udp"},
 		{Port: 123, Protocol: "UDP"}, // case-insensitive
 	}