fix: make Supabase optional and add assetPrefix support

- lib/supabase.ts: Return null when credentials missing instead of crash
- next.config.js: Add assetPrefix and basePath for VibeCoder proxy
- package.json: Use generic template name (v0.2.0)

lib/supabase.ts

@@ -1,6 +1,14 @@
-import { createClient } from '@supabase/supabase-js';
+import { createClient, SupabaseClient } from '@supabase/supabase-js';
 
-const supabaseUrl = process.env.NEXT_PUBLIC_SUPABASE_URL!;
-const supabaseAnonKey = process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!;
+const supabaseUrl = process.env.NEXT_PUBLIC_SUPABASE_URL;
+const supabaseAnonKey = process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY;
 
-export const supabase = createClient(supabaseUrl, supabaseAnonKey);
+// Create client only if credentials are available
+// This allows the app to run without Supabase for basic previews
+export const supabase: SupabaseClient | null = 
+  supabaseUrl && supabaseAnonKey
+    ? createClient(supabaseUrl, supabaseAnonKey)
+    : null;
+
+// Helper to check if Supabase is configured
+export const isSupabaseConfigured = (): boolean => supabase !== null;