[Enhancement] Add an offline-capable error state for the SESSION_EXPIRED request rejection

CONTRIBUTING.md

@@ -123,3 +123,131 @@ Husky hooks enforce a baseline before changes reach CI:
 
 You can bypass the hooks for a one-off push with `git push --no-verify`, but note
 that the same checks still run in CI and will block the pull request.
+
+
+
+# Contributing to TeachLink Mobile
+
+Thank you for contributing to TeachLink Mobile!
+
+## Pull Request Guidelines
+
+When submitting a Pull Request, you must fill out the provided PR template.  
+The template ensures that all necessary considerations are accounted for before merge.
+
+Please review the `.github/pull_request_template.md` which includes:
+- **Summary & Type of Change**: Describe what the PR does.
+- **Testing Done**: List the tests performed.
+- **Security Considerations**: Address concerns like secure data storage, token handling, input validation, and deep link handling.
+- **Performance Considerations**: Address concerns like hook optimization (`useCallback`, `useMemo`), `FlatList` optimization, and asynchronous patterns.
+- **Checklist**: General checks, including checking whether an Architectural Decision Record (ADR) is needed.
+
+## Fast-Fail Syntax Gate
+
+We have a dedicated **Syntax Gate** workflow (`.github/workflows/syntax.yml`) that runs on every pull request `opened` or `synchronize` event.
+
+- Checks TypeScript compiler errors (`tsc --noEmit`) and ESLint (`eslint --max-warnings=0`)
+- Optimized to complete in **under 90 seconds** using caching
+- Required for branch protection — PRs cannot be merged if it fails
+- Run checks locally before pushing to avoid CI failures
+
+## Architecture
+
+The intended module structure, layering and dependency direction are documented
+in [docs/ARCHITECTURE.md](docs/ARCHITECTURE.md). The layering is enforced locally
+and in CI with dependency-cruiser:
+
+```bash
+npm run architecture:check
+```
+
+Read the architecture doc before adding a new module — the codebase already has
+a single canonical implementation for error handling, logging, location, course
+progress, sync conflict resolution, and feature flags, and duplicating one of
+these is a review blocker.
+
+## Structured Logging
+
+**Never use `console.*` in `src/`.** The ESLint `no-console` rule is set to `error`, and CI will fail if any `console.*` call is introduced. Use `src/utils/logger` instead.
+
+### Why structured logging?
+
+`console.log` output is unstructured, always-on, and leaks information in production builds. `logger` gives you:
+- Log level filtering (only `error` and `warn` in production)
+- Consistent metadata (timestamp, component context)
+- A single place to redirect logs to remote monitoring (e.g. Sentry, Datadog)
+
+### Log level guide
+
+| Level | Method | When to use |
+|---|---|---|
+| **error** | `logger.error(msg, err?)` | Unexpected failures that need immediate attention. Always include the `Error` object as the second argument. |
+| **warn** | `logger.warn(msg, ctx?)` | Recoverable issues or deprecated code paths that should be investigated. |
+| **info** | `logger.info(msg, ctx?)` | Key lifecycle events: component mount/unmount, navigation, background sync. Keep them meaningful, not noisy. |
+| **debug** | `logger.debug(msg, ctx?)` | Verbose detail useful during development only. Stripped from production builds. |
+| **component** | `logger.component(name, event, ctx?)` | Convenience wrapper for component lifecycle events — equivalent to `info` with a standardised format. |
+
+### Examples
+
+```ts
+// ✅ Correct
+import { logger } from '../../utils/logger';
+
+logger.component('MyScreen', 'Mounted', { userId });
+logger.info('Resuming lesson from position:', position);
+logger.warn('Quiz data missing for section:', sectionId);
+logger.error('Failed to sync progress:', error);
+
+// ❌ Incorrect — will fail CI
+console.log('user mounted', userId);
+console.error('sync failed', error);
+```
+
+### Audit
+
+CI runs a console violation scan on every push. To run it locally:
+
+```bash
+grep -rn "console\." src/ --include='*.ts' --include='*.tsx'
+```
+
+Zero matches is the expected output.
+
+## Local Quality Checks
+
+You can run the checks locally:
+
+```bash
+# Run ESLint linting
+npm run lint
+
+# Check formatting
+npm run format:check
+
+# Run TypeScript type check (same check CI runs)
+npm run typecheck
+
+# Continuously re-run the type check as you edit
+npm run typecheck:watch
+```
+
+### Lint warning budget
+
+Lint warnings are capped by a single ratcheting budget in `lint-budget.json`
+(`maxWarnings`), enforced by `ci.yml`. There is exactly one lint gate in CI.
+
+- `npm run lint:budget` — fails if the current warning count exceeds the budget,
+  or if the budget is looser than the measured count (so the ceiling can only
+  decrease over time).
+- `npm run lint:budget:record` — measures the warning count and records it as the
+  new, lower budget. Run and commit this after removing warnings so the budget
+  ratchets down instead of silently growing.
+### Git hooks
+
+Husky hooks enforce a baseline before changes reach CI:
+
+- **`pre-commit`** — runs `lint-staged` (Prettier + ESLint) on staged files.
+- **`pre-push`** — runs `npm run typecheck` so type errors are caught before push.
+
+You can bypass the hooks for a one-off push with `git push --no-verify`, but note
+that the same checks still run in CI and will block the pull request.