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

lib/models.dart

@@ -1,18 +1,18 @@
 import 'package:objectbox/objectbox.dart';
 
 /// User entity - works for both HOME and GUEST servers
-/// 
+///
 /// On HOME server:
 /// - isLocal = true
 /// - stores password, encrypted private key
 /// - this is where identity lives
-/// 
+///
 /// On GUEST server:
 /// - isLocal = false
 /// - homeServer contains the URL of user's home
 /// - publicKey cached for verification
-@Entity()
-class User {
+@Entity(uid: 3848231140411393897)
+class ChatUser {
   @Id()
   int id = 0;
 
@@ -37,7 +37,8 @@ class User {
 
   // Server relationship
   bool isLocal; // true = this is their home server
-  String? homeServer; // if guest, where is their home? (e.g., "https://my.server.com")
+  String?
+      homeServer; // if guest, where is their home? (e.g., "https://my.server.com")
 
   // Server-specific
   List<String> roles; // ["admin", "moderator", "member"]
@@ -48,7 +49,7 @@ class User {
   @Property(type: PropertyType.date)
   DateTime? lastSyncedAt; // When profile was last refreshed from home
 
-  User({
+  ChatUser({
     required this.userId,
     required this.username,
     required this.publicKey,
@@ -68,8 +69,8 @@ class User {
         lastSyncedAt = lastSyncedAt;
 }
 
-@Entity()
-class Channel {
+@Entity(uid: 2663861829934850300)
+class ChatChannel {
   @Id()
   int id = 0;
 
@@ -81,15 +82,15 @@ class Channel {
   @Property(type: PropertyType.date)
   DateTime createdAt;
 
-  Channel({
+  ChatChannel({
     required this.name,
     this.description,
     DateTime? createdAt,
   }) : createdAt = createdAt ?? DateTime.now();
 }
 
-@Entity()
-class Message {
+@Entity(uid: 2697867424319168785)
+class ChatMessage {
   @Id()
   int id = 0;
 
@@ -112,7 +113,7 @@ class Message {
   @Property(type: PropertyType.date)
   DateTime? editedAt;
 
-  Message({
+  ChatMessage({
     required this.channelId,
     required this.authorLocalId,
     required this.authorUserId,