fix : added error handling and input validation to trackActivity utility

[tmdeveloper007]

Closes (upstream issues disabled — no issue created).

Summary of What Has Been Done:
Added input validation and comprehensive error handling to the trackActivity utility in lib/activity.js. The function previously had no validation on userId or type parameters and no try/catch, meaning invalid inputs or database errors would cause unhandled promise rejections silently. Now the function validates that userId and type are non-empty strings before making any database calls, wraps all Supabase operations in try/catch, and logs errors gracefully instead of crashing.

Changes Made:

• lib/activity.js: add input validation, try/catch around all async operations, explicit error logging
• security-tests/activity-util.test.cjs: new file covering all validation branches

Impact it Made:

• Prevents unhandled promise rejections from trackActivity calls with bad inputs
• Provides warning logs for invalid inputs instead of crashing the calling component
• Adds test coverage for the validation logic

Note: Please assign this PR to the tmdeveloper007 account.