feat: add database support, conversation sidebar, and improve chat streaming

- Update .gitignore to exclude database files, extensions, and .cursor directory
- Enhance chat streaming API with safe enqueue and close functions to prevent errors
- Integrate ConversationSidebar component into ClientHome for better UI
- Add dependencies like better-sqlite3 and esbuild packages for database functionality

This commit introduces database persistence for conversations, improves error handling in streaming responses, and adds a sidebar for managing chats, enhancing overall app robustness and user experience.

database/repositories/message.ts

@@ -0,0 +1,86 @@
+import Database from "better-sqlite3";
+import type { ChatRole } from "@/lib/chat";
+
+export interface Message {
+  id: string;
+  conversation_id: string;
+  role: ChatRole;
+  content: string;
+  timestamp: number;
+}
+
+export class MessageRepository {
+  constructor(private db: Database.Database) {}
+
+  create(conversationId: string, role: ChatRole, content: string): string {
+    const id = crypto.randomUUID();
+
+    this.db
+      .prepare(
+        `
+      INSERT INTO messages (id, conversation_id, role, content, timestamp)
+      VALUES (?, ?, ?, ?, ?)
+    `
+      )
+      .run(id, conversationId, role, content, Date.now());
+
+    return id;
+  }
+
+  findByConversation(conversationId: string): Message[] {
+    return this.db
+      .prepare(
+        `
+      SELECT * FROM messages 
+      WHERE conversation_id = ?
+      ORDER BY timestamp ASC
+    `
+      )
+      .all(conversationId) as Message[];
+  }
+
+  findById(id: string): Message | null {
+    return this.db
+      .prepare(
+        `
+      SELECT * FROM messages WHERE id = ?
+    `
+      )
+      .get(id) as Message | null;
+  }
+
+  updateContent(id: string, content: string): void {
+    this.db
+      .prepare(
+        `
+      UPDATE messages 
+      SET content = ?
+      WHERE id = ?
+    `
+      )
+      .run(content, id);
+  }
+
+  delete(id: string): void {
+    this.db.prepare("DELETE FROM messages WHERE id = ?").run(id);
+  }
+
+  deleteByConversation(conversationId: string): void {
+    this.db
+      .prepare("DELETE FROM messages WHERE conversation_id = ?")
+      .run(conversationId);
+  }
+
+  countByConversation(conversationId: string): number {
+    const result = this.db
+      .prepare(
+        `
+      SELECT COUNT(*) as count FROM messages 
+      WHERE conversation_id = ?
+    `
+      )
+      .get(conversationId) as { count: number };
+
+    return result.count;
+  }
+}