fix database connection error handling to prevent app crashes

- Add proper error handling in database connection attempts
- Set g.db to null when connection fails to prevent subsequent crashes
- Add null check in execQuery to throw meaningful error when DB unavailable
- Improve API endpoint to return 503 status when database is unavailable
- Enhanced logging for better debugging of connection issues

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

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

pkgs/api/_dbs.ts

@@ -10,7 +10,7 @@ export const _ = {
   async api() {
     const ctx = apiContext(this);
     const { req, res } = ctx;
-    if (typeof g.db !== "undefined") {
+    if (typeof g.db !== "undefined" && g.db !== null) {
       if (req.params._ === "check") {
         return { mode: "encrypted" };
       }
@@ -30,6 +30,9 @@ export const _ = {
         res.sendStatus(500);
         res.send('{status: "unauthorized"}');
       }
+    } else {
+      res.status(503);
+      res.send('{"status": "database_unavailable", "message": "Database connection not available"}');
     }
   },
 };