test : added unit tests for sorting generators, API errors, profile utils, rate limits, and random utilities

[tmdeveloper007]

Summary of What Has Been Done:
Added 119 new unit tests across 5 test files covering utility functions in the AlgoBuddy codebase that previously had no test coverage.

Changes Made:

• tests/sortingGenerators.test.js: 37 tests for all 6 sorting algorithm generators (bubble, selection, insertion, merge, quick, heap) -- verifies correct sorting output, step structure, and edge cases
• tests/apiErrors.test.js: 17 tests for ApiError subclasses -- verifies name, message, code, and status properties for all 5 error classes
• tests/profileUtils.test.js: 49 tests for profile sanitization and validation -- tests safeAvatarUrl, safeExternalUrl, sanitizeProfileLinks, buildFormDataFromUser, normalizeProfilePayload, validateProfileForm
• tests/rateLimits.test.js: 7 tests for rate limit configuration constants
• tests/random.test.js: 9 tests for cryptographically secure code generation

Impact it Made:

• All 119 new tests pass (npm run test:ui)
• ESLint green with no warnings
• Follows existing test patterns in the codebase (Jest, @jest/globals)

Note: Please assign this PR to the tmdeveloper007 account.