feat: implement Design Buddy AI interior design application

- Replace boilerplate with complete Design Buddy application
- Add AI-powered room design generation using Google Gemini SDK
- Implement user authentication with Google OAuth via Better Auth
- Create credit system with 30 free credits for new users
- Build image upload interface with drag-and-drop functionality
- Add room type and design style selection (Living Room, Kitchen, etc.)
- Implement AI generation with geographical restriction handling
- Add credit refund system for API failures
- Create responsive landing page with feature sections
- Replace all branding and navigation with Design Buddy theme
- Add complete user dashboard with real-time credit balance
- Implement download functionality for generated designs

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

docs/technical/ai/google/image-editing.md

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+// To run this code you need to install the following dependencies:
+// npm install @google/genai mime
+// npm install -D @types/node
+
+import {
+  GoogleGenAI,
+} from '@google/genai';
+import mime from 'mime';
+import { writeFile } from 'fs';
+
+function saveBinaryFile(fileName: string, content: Buffer) {
+  writeFile(fileName, content, 'utf8', (err) => {
+    if (err) {
+      console.error(`Error writing file ${fileName}:`, err);
+      return;
+    }
+    console.log(`File ${fileName} saved to file system.`);
+  });
+}
+
+async function main() {
+  const ai = new GoogleGenAI({
+    apiKey: process.env.GEMINI_API_KEY,
+  });
+  const config = {
+    responseModalities: [
+        'IMAGE',
+        'TEXT',
+    ],
+  };
+  const model = 'gemini-2.5-flash-image-preview';
+  const contents = [
+    {
+      role: 'user',
+      parts: [
+        {
+          text: `INSERT_INPUT_HERE`,
+        },
+      ],
+    },
+  ];
+
+  const response = await ai.models.generateContentStream({
+    model,
+    config,
+    contents,
+  });
+  let fileIndex = 0;
+  for await (const chunk of response) {
+    if (!chunk.candidates || !chunk.candidates[0].content || !chunk.candidates[0].content.parts) {
+      continue;
+    }
+    if (chunk.candidates?.[0]?.content?.parts?.[0]?.inlineData) {
+      const fileName = `ENTER_FILE_NAME_${fileIndex++}`;
+      const inlineData = chunk.candidates[0].content.parts[0].inlineData;
+      const fileExtension = mime.getExtension(inlineData.mimeType || '');
+      const buffer = Buffer.from(inlineData.data || '', 'base64');
+      saveBinaryFile(`${fileName}.${fileExtension}`, buffer);
+    }
+    else {
+      console.log(chunk.text);
+    }
+  }
+}
+
+main();