feat: integrate vectordb for note embeddings

- Added `vectordb` as a dependency in `package.json`.
- Implemented `embedText` function in `src/main/ai/embeddings.ts` to handle text embeddings using GitHub Copilot OAuth token or OpenAI token.
- Created `vectordb.ts` for managing LanceDB connection and embedding notes with upsert strategy.
- Updated `index.ts` to initialize vector database and migrate existing notes on app ready.
- Modified `router/index.ts` to fire-and-forget embedding calls on note creation and updates.
- Enhanced `progress.txt` with detailed implementation notes and learnings regarding the integration.

vite.main.config.mts

@@ -17,6 +17,7 @@ export default defineConfig({
         '@langchain/anthropic',
         '@langchain/langgraph-checkpoint',
         '@langchain/langgraph-sdk',
+        'vectordb',
       ],
       output: {
         entryFileNames: 'main.js',