fix: comprehensive codebase improvements and bug fixes

[Pranav-Karra-3301]

Security:

• Fix query parameter injection by adding URL encoding
• Guard process.env access for non-Node environments

Bug Fixes:

• Fix rate limiter rejecting wrong object (was workItem, now err)
• Fix array Link headers breaking pagination
• Add MAX_RETRIES=5 to prevent infinite retry loops
• Add parseError property to track JSON parse failures

Breaking Circular Dependency:

• Extract CanvasApiResponse to src/canvasApiResponse.ts

Type Safety:

• Make CanvasApiResponse generic: CanvasApiResponse
• Add generic parameters to get(), request(), listPages(), listItems()

New Exports:

• CanvasApiResponse, QueryParams, RequestOptions
• CanvasApiTimeoutError, CanvasApiPaginationError
• ExtendedGenerator

Documentation:

• Add CHANGELOG.md with version history
• Add CONTRIBUTING.md with dev setup and PR guidelines
• Add .env.example template
• Add JSDoc to all public methods
• Expand README with rate limiting, debug logging, TypeScript types

Testing:

• Add src/canvasApiError.test.ts (9 tests)
• Add integration-tests/pagination.test.ts (9 tests)
• Add integration-tests/error-handling.test.ts (14 tests)
• Expand extendedGenerator tests (15 new tests)

Dependencies:

• Update undici 6.19.2 → 6.23.0
• Update typescript 4.9.5 → 5.9.3
• Update prettier 2.8.2 → 3.8.1
• Remove unused: fast-csv, msw, ora, tempy, @types/create-test-server

Improvements:

• Add debug logging via CANVAS_API_DEBUG=true
• Add proactive rate limit header checking
• Update examples to use .json instead of deprecated .body
• Add custom-formdata.js example