Add UI editing for local DNS zones

Local zones were only editable as mounted files, so operators could not manage DNS entries from the console. Add a Local zones editor backed by a shared Kubernetes ConfigMap, validate master files before saving, scope the pod service account to that ConfigMap, and reload changed zones on every replica while flushing stale cache entries.

web/src/App.tsx

@@ -19,6 +19,7 @@ import Dashboard from './pages/Dashboard.tsx'
 import Domains from './pages/Domains.tsx'
 import Login from './pages/Login.tsx'
 import Logs from './pages/Logs.tsx'
+import LocalZones from './pages/LocalZones.tsx'
 import NotFound from './pages/NotFound.tsx'
 import Settings from './pages/Settings.tsx'
 import Upstreams from './pages/Upstreams.tsx'
@@ -50,6 +51,7 @@ function AppRoutes() {
       <Route path="/" element={<Dashboard />} />
       <Route path="/blocklists" element={<Blocklists />} />
       <Route path="/domains" element={<Domains />} />
+      <Route path="/local-zones" element={<LocalZones />} />
       <Route path="/clients" element={<Clients />} />
       <Route path="/upstreams" element={<Upstreams />} />
       <Route path="/logs" element={<Logs />} />