Add total litter collected display to user profile

- Updated backend userService to calculate total litter collected across all attended events
- Added totalLitterCollected field to UserProfile interface
- Added new statistics card showing total litter collected in kg
- Updated profile grid layout to accommodate 5 statistics cards
- Displays litter collected with 1 decimal place precision

server/prisma/migrations/20251118183315_add_attendee_contributions/migration.sql

@@ -0,0 +1,4 @@
+-- AlterTable
+ALTER TABLE `event_registrations` 
+ADD COLUMN `litter_collected` DECIMAL(10, 2) NULL,
+ADD COLUMN `contribution_note` TEXT NULL;