Register Exception Handlers and Standardize Error Responses

Problem

Exception handlers are defined in exception_handlers.py but are not imported in main.py, so they are not being registered with the application.

Error handling also needs to be standardized:

• Web requests should render an HTML error page instead of returning JSON.
• Errors should use a consistent HTTPException format.

Proposed Changes

• Register the exception handlers in main.py.

• Handle:

  • StarletteHTTPException - HTTP errors (400, 401, 403, 404, etc.)
  • RequestValidationError - validation errors (422)
  • Exception - unexpected errors (500)

• Use a consistent HTTPException structure with the appropriate status code and error message.

• Render error.html for web requests.

• Add templates/error.html extending _layout.html.

Expected Behavior

• Errors are handled consistently across the application.
• Web errors render a consistent HTML error page.
• API errors return the appropriate HTTP error response.

Start by reading exception_handlers.py and main.py to trace the existing handlers and application setup. Add the error template at templates/error.html, extending _layout.html, and verify the listed HTTP, validation, and unexpected errors produce HTML for web requests and appropriate responses for API requests.