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.

hooks/useCopyPrefs.ts

@@ -0,0 +1,28 @@
+"use client";
+
+import { useCallback, useEffect, useState } from "react";
+
+export type CopyMode = "markdown" | "text";
+
+const KEY = "ollahub-copy-mode";
+
+export function useCopyPrefs() {
+  const [copyMode, setCopyModeState] = useState<CopyMode>("markdown");
+
+  useEffect(() => {
+    if (typeof window === "undefined") return;
+    const saved = localStorage.getItem(KEY) as CopyMode | null;
+    if (saved === "markdown" || saved === "text") {
+      setCopyModeState(saved);
+    }
+  }, []);
+
+  const setCopyMode = useCallback((mode: CopyMode) => {
+    setCopyModeState(mode);
+    if (typeof window !== "undefined") {
+      localStorage.setItem(KEY, mode);
+    }
+  }, []);
+
+  return { copyMode, setCopyMode };
+}