[1sakshm]

Description

Follow-up to #731/#732. When Open-Meteo itself failed (down, 429 rate limit, or no network), GET /weather/forecast returned 500 INTERNAL_ERROR, the same code as a crash inside FireForm.

openmeteo_requests wraps every upstream failure in OpenMeteoRequestsError, so the route now catches it before the generic handler:

Situation	Before	After
Open-Meteo error / unreachable	500 INTERNAL_ERROR	502 WEATHER_FETCH_FAILED (message kept)
Any other exception	500	500 (unchanged)

This matches how the address lookup reports Nominatim failures (#741). No frontend change needed: the weather modal already shows the backend's message.

Fixes #742

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• Added to TestWeatherEndpoints in tests/test_api.py:
  • test_forecast_upstream_error_is_502: openmeteo_requests.Client.weather_api raises OpenMeteoRequestsError → 502 WEATHER_FETCH_FAILED with the original message. Fails on development (500).
  • test_forecast_unexpected_error_is_500: any other exception still gives 500.
• Full suite: python -m pytest tests/ → 315 passed
• ruff check app/ → all checks passed

Test Configuration:

• Python version: 3.11
• Docker/Compose version: N/A (tests run locally)
• OS: Windows 11

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• The Lint workflow check passes on this PR ✅
• The Tests workflow check passes on this PR ✅