Add daily automatic database backup to GitHub

- Remove data/ from .gitignore (keep WAL/SHM excluded)
- Add backup.sh script: commits and pushes DB changes daily
- Cron job at 3:00 AM: /var/www/html/dispensa/backup.sh
- Include initial database snapshot

.gitignore

@@ -1,8 +1,9 @@
 # Environment variables (secrets)
 .env
 
-# SQLite database
-data/
+# SQLite WAL/SHM temp files
+data/*.db-wal
+data/*.db-shm
 
 # SSL CA cert (local only)
 ca.crt