normalize project structure: src/client + src/server + src/shared

- restructure from src/ + server/ to src/client/ + src/server/ + src/shared/
- switch backend runtime from Node (tsx) to Bun
- merge server/package.json into root, remove @hono/node-server + tsx
- convert server @/ imports to relative paths
- standardize biome config (lineWidth 80, quoteStyle double)
- add CLAUDE.md, .env.example at root
- update vite.config, tsconfig, deploy.sh for new structure

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.env.example

@@ -0,0 +1,5 @@
+DATABASE_URL=postgres://user:password@localhost:5432/abgeordnetenwatch
+PORT=3000
+VAPID_PUBLIC_KEY=
+VAPID_PRIVATE_KEY=
+VAPID_SUBJECT=mailto:your-email@example.com