feat: Domain-keyed service registration model

Rewrite the service registration model per the architecture plan:

Model changes:
- Domain is the unique key (removed Name field)
- Removed ExtraDomains — each domain is its own registration
- Removed SourceNode, BackendStatic, ReachOff
- Added Subdomains bool for wildcard matching control
- Files stored as <domain_with_underscores>.yaml
- API routes: /services/{domain:.+} (regex for dots in path)
- Added DeregisterBySource for cleanup before re-registration

Reconciliation changes:
- No ExtraDomains iteration — each service IS one domain
- reach:internal → sets InternalDomain (generates local=/)
- reach:public → sets Domain (no local=/)
- tcp-passthrough → DNS points to backend IP
- http → DNS points to Central IP

All 22 tests pass (9 manager + 8 handler + 5 config/cert).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

internal/api/v1/handlers.go

@@ -113,7 +113,6 @@ func (api *API) RegisterSelf(port int) {
 	}
 
 	svc := services.Service{
-		Name:   "wild-central",
 		Source: "wild-central",
 		Domain: domain,
 		Backend: services.Backend{
@@ -251,12 +250,13 @@ func (api *API) RegisterRoutes(r *mux.Router) {
 	r.HandleFunc("/api/v1/cloudflare/zone", api.CloudflareGetZoneID).Methods("GET")
 	r.HandleFunc("/api/v1/cloudflare/zone", api.CloudflareSetZoneID).Methods("POST")
 
-	// Service registration
+	// Service registration — domain is the unique key
 	r.HandleFunc("/api/v1/services", api.ServicesListAll).Methods("GET")
 	r.HandleFunc("/api/v1/services", api.ServicesRegister).Methods("POST")
-	r.HandleFunc("/api/v1/services/{name}", api.ServicesGet).Methods("GET")
-	r.HandleFunc("/api/v1/services/{name}", api.ServicesUpdate).Methods("PATCH")
-	r.HandleFunc("/api/v1/services/{name}", api.ServicesDeregister).Methods("DELETE")
+	r.HandleFunc("/api/v1/services/deregister", api.ServicesDeregisterBySource).Methods("DELETE")
+	r.HandleFunc("/api/v1/services/{domain:.+}", api.ServicesGet).Methods("GET")
+	r.HandleFunc("/api/v1/services/{domain:.+}", api.ServicesUpdate).Methods("PATCH")
+	r.HandleFunc("/api/v1/services/{domain:.+}", api.ServicesDeregister).Methods("DELETE")
 
 	// SSE events
 	r.HandleFunc("/api/v1/events", api.GlobalEventStream).Methods("GET")