Implement chat server auth, models, handlers, and docs context

lib/src/handlers/public_handlers.dart

@@ -1,18 +1,28 @@
-import 'package:chat_server/models.dart';
 import 'package:chat_server/objectbox.g.dart';
 import 'package:relic/relic.dart';
 
+import '../../config/config.dart';
+import '../state/app_state.dart';
 import '../utils/extensions.dart';
 
 /// Public endpoint for cross-server identity verification
 /// Called by other servers to verify a user's public key
-/// 
+///
 /// GET /.well-known/users/{username}
 /// Returns: { userId, publicKey, username, displayName, avatarUrl }
-Future<Response> publicUserHandler(Request req, String username) async {
-  final query = userBox.query(
-    User_.username.equals(username) & User_.isLocal.equals(true),
-  ).build();
+Future<Response> publicUserHandler(Request req) async {
+  final username = req.rawPathParameters[#username];
+  if (username == null) {
+    return Response.badRequest(
+      body: Body.fromString('Username required'),
+    );
+  }
+
+  final query = userBox
+      .query(
+        ChatUser_.username.equals(username) & ChatUser_.isLocal.equals(true),
+      )
+      .build();
 
   final user = query.findFirst();
   query.close();
@@ -39,13 +49,22 @@ Future<Response> publicUserHandler(Request req, String username) async {
 
 /// Public endpoint to verify a user exists
 /// Lightweight check without full profile
-/// 
+///
 /// GET /.well-known/verify/{userId}
 /// Returns: { exists, userId, publicKey }
-Future<Response> publicVerifyHandler(Request req, String userId) async {
-  final query = userBox.query(
-    User_.userId.equals(userId) & User_.isLocal.equals(true),
-  ).build();
+Future<Response> publicVerifyHandler(Request req) async {
+  final userId = req.rawPathParameters[#userId];
+  if (userId == null) {
+    return Response.badRequest(
+      body: Body.fromString('userId required'),
+    );
+  }
+
+  final query = userBox
+      .query(
+        ChatUser_.userId.equals(userId) & ChatUser_.isLocal.equals(true),
+      )
+      .build();
 
   final user = query.findFirst();
   query.close();
@@ -70,7 +89,7 @@ Future<Response> publicVerifyHandler(Request req, String userId) async {
 }
 
 /// Public server info
-/// 
+///
 /// GET /.well-known/server
 /// Returns: { serverHost, serverName, version }
 Future<Response> publicServerInfoHandler(Request req) async {