Add Email Validation Support (EmailStr + email-validator)

[Mattsface]

Add Email Validation Support (EmailStr + email-validator)

🎯 Objective

Restore proper email validation in auth models by reintroducing EmailStr with correct email-validator dependency configuration.

📋 Background

During initial scaffold setup (Issue #1), we temporarily replaced EmailStr with str in auth models to unblock Docker builds due to missing email-validator dependency. This sub-issue restores proper email validation.

🔧 Technical Requirements

Dependencies

• Add email-validator to pyproject.toml dependencies
• OR use pydantic = { version = "^2.11", extras = ["email"] }
• Ensure dependency resolves correctly in Poetry lock file
• Verify package installs in Docker image

Code Changes

# In corner_pocket_backend/api/v1/auth.py
# Change from:
class RegisterIn(BaseModel):
    email: str  # Current temporary fix
    
# Back to:
from pydantic import EmailStr
class RegisterIn(BaseModel):
    email: EmailStr  # Proper validation

Docker Verification

• Docker build succeeds with email-validator
• poetry run pip list shows email-validator installed
• Container runs without import errors

✅ Acceptance Criteria

1. Email Validation Works

   # Valid email - should succeed
   curl -X POST http://localhost:8000/api/v1/auth/register \
     -H 'Content-Type: application/json' \
     -d '{"email":"test@example.com","handle":"test","display_name":"Test","password":"pw"}'
   
   # Invalid email - should return 422 validation error
   curl -X POST http://localhost:8000/api/v1/auth/register \
     -H 'Content-Type: application/json' \
     -d '{"email":"invalid-email","handle":"test","display_name":"Test","password":"pw"}'

2. Build & Deploy

   • Docker builds without cache successfully
   • No import errors on container startup
   • All existing smoke tests still pass

3. Dependencies

   • poetry install works locally
   • poetry run python -c "from pydantic import EmailStr; print('OK')" succeeds
   • Docker image size doesn't increase significantly

🔄 Implementation Options

Option A: Direct dependency

[tool.poetry.dependencies]
email-validator = "^2.3.0"

Option B: Pydantic extra (recommended)

[tool.poetry.dependencies]
pydantic = { version = "^2.11", extras = ["email"] }

Option C: Force install in Dockerfile

RUN poetry install --no-root --only main \
 && poetry run pip install email-validator

📝 Files to Update

• pyproject.toml - Add dependency
• corner_pocket_backend/api/v1/auth.py - Restore EmailStr imports/usage
• Verify no other files use email fields

⚠️ Risks

• Dependency resolution conflicts (low risk)
• Docker layer caching may need --no-cache rebuild
• Regression in auth endpoints (mitigated by testing)

🧪 Testing

• Unit test: valid email passes validation
• Unit test: invalid email returns 422
• Integration: full auth flow still works
• Docker: build and smoke test