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.

app/api/preferences/route.ts

@@ -0,0 +1,42 @@
+import { NextRequest, NextResponse } from "next/server";
+import { getPreferences, setPreferences } from "@/lib/preferences";
+
+// Estrutura de preferências
+type UserPreferences = {
+  selectedModel: string | null;
+  systemPrompt: string;
+  device: "auto" | "cpu" | "gpu";
+  gpuIndex: number;
+  numGpu: number;
+};
+
+// GET - Buscar preferências
+export async function GET(request: NextRequest) {
+  try {
+    const userId = "default"; // Pode ser expandido para multi-usuário
+    const prefs = await getPreferences(userId);
+    return NextResponse.json(prefs);
+  } catch (error) {
+    console.error("Erro ao buscar preferências:", error);
+    return NextResponse.json(
+      { error: "Erro interno do servidor" },
+      { status: 500 }
+    );
+  }
+}
+
+// POST - Salvar preferências
+export async function POST(request: NextRequest) {
+  try {
+    const userId = "default";
+    const prefs = await request.json();
+    await setPreferences(userId, prefs);
+    return NextResponse.json({ success: true });
+  } catch (error) {
+    console.error("Erro ao salvar preferências:", error);
+    return NextResponse.json(
+      { error: "Erro interno do servidor" },
+      { status: 500 }
+    );
+  }
+}