Add scan history, quick add button, camera manual UPC test, and warning pop up

[oerivas-star]

Add scan history, quick add button, camera manual UPC test, and warning

Changes

• Added scan history storage using Firestore subcollection (users/{userId}/scans)
• Added endpoint to fetch recent scans
• Updated camera screen:
  • Saves scans automatically
  • Manual UPC input for testing
  • Warning modal for allergens/intolerances
• Updated home screen:
  • Displays real recent scans
  • Quick Add modal
  • Improved bottom navigation
• Updated profile screen:
  • Fetches real user data
  • Added working logout button

Notes

• Manual UPC testing added for web since Expo Go camera is currently unreliable
• Backend now handles scan persistence automatically

Future Work

• Improve scan history UI
• Add deletion/editing for scans
• Improve mobile camera testing setup

Also fixing the edit functions
there was a bug in the edit that i totatlly forgot about but its good now

[Logan-Roche]

lgtm