[type](scope): Short description (max 72 chars)

[Optional body - what and why, not how]

[Optional footer - issue references, breaking changes]

Refs: #[ISSUE_NUMBER]

feat(auth): Add user registration endpoint

Implement POST /api/users/register with email validation,
password hashing, and duplicate detection.

- Validates email format and uniqueness
- Hashes password with bcrypt
- Returns user object without password

Refs: #123

fix(auth): Prevent redirect loop on expired session

Session expiry was triggering redirect to login, which
checked session, found expired, and redirected again.

Now clears session cookie before redirecting.

Refs: #456

test(auth): Add integration tests for registration

Cover success case, duplicate email, invalid format,
and weak password scenarios.

Refs: #123

# Stage specific files
git add src/auth/register.ts
git add src/auth/register.test.ts
git commit -m "feat(auth): Add registration endpoint"

# Stage next logical unit
git add src/auth/login.ts
git add src/auth/login.test.ts
git commit -m "feat(auth): Add login endpoint"

# Run tests
pnpm test

# Check build
pnpm build

# Check types
pnpm typecheck

# Check lint
pnpm lint

# Review what changed
git diff

# Stage specific files
git add [specific files]

# Or stage interactively
git add -p

# See what will be committed
git diff --staged

# Short message (if simple)
git commit -m "fix(auth): Handle null user in session check"

# Long message (if complex)
git commit
# Opens editor for full message

# Check commit looks right
git show --stat

# Verify tests still pass
pnpm test

refactor(api): Extract validation middleware

Validation logic was duplicated across 12 endpoints.
Extracted to reusable middleware that can be composed.

Alternative considered: validation library.
Rejected because our rules are domain-specific.

fix(data): Use optimistic locking for updates

Race condition was causing lost updates when two users
edited the same record simultaneously.

BREAKING CHANGE: Update operations now require
version field in request body.

# In commit message
Refs: #123

# Or if commit closes the issue
Closes: #123

# Amend last commit (before push only!)
git add forgotten-file.ts
git commit --amend

# Create a new commit that undoes the change
git revert [commit-sha]

# DON'T rewrite history on shared branches
# DON'T force push to fix mistakes