feat: migrate to Bun-native, fix Planner task dates, remove hardcoded test values

- Remove dotenv dependency, implement lightweight Bun-native env loader
- Replace Node.js fs/path with Bun file APIs (Bun.file, Bun.write)
- Fix Planner task creation to use form's due date with proper UTC handling
- Make table name, Planner assignee configurable via activeConfig and env vars
- Remove all hardcoded test values for PROD readiness
- Update NOTES.md with PROD mode checklist

package.json

@@ -9,7 +9,6 @@
   },
   "dependencies": {
     "@microsoft/microsoft-graph-client": "^3.0.7",
-    "dotenv": "^17.2.3",
     "hono": "^4.10.8",
     "pocketbase": "^0.26.5"
   },