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/api/v1/handlers_haproxy.go

@@ -47,7 +47,7 @@ func (api *API) HaproxyRestart(w http.ResponseWriter, r *http.Request) {
 // HaproxyGenerate regenerates HAProxy config from all WC instance data and custom routes,
 // then updates nftables to match. Both operations happen together so ports stay in sync.
 func (api *API) HaproxyGenerate(w http.ResponseWriter, r *http.Request) {
-	api.reconcileNetworking()
+	api.reconciler.Reconcile()
 
 	content, err := api.haproxy.ReadConfig()
 	if err != nil {
@@ -68,5 +68,3 @@ func (api *API) HaproxyStats(w http.ResponseWriter, r *http.Request) {
 	}
 	respondJSON(w, http.StatusOK, map[string]any{"backends": stats})
 }
-
-