UI: Add option to configure default task log source

[AyushCoder9]

Description

Introduces a new configuration setting api.default_ui_log_source to specify a default log source for reading task logs in the web UI instead of defaulting strictly to "All Sources".

• Backend:

  • Added default_ui_log_source parameter within airflow/config_templates/config.yml under the [api] section.
  • Expose the parameter in the general UI payload models inside datamodels/ui/config.py and returned aggregator routing endpoints at routes/ui/config.py.
  • Regenerated UI openapi types to support the strictly typed fallback references.

• Frontend:

  • Modified Logs.tsx query logic to fall back accurately on useConfig defaults when query search parameters for SOURCE are empty.
  • Adapted TaskLogHeader.tsx visually select mapping default layouts to represent the configured fallback parameters neatly.
  • Successfully verified linting and all unit tests passed flawlessly with 0 errors natively.

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closes: #64159

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[boring-cyborg]

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[bbovenzi]

Would love a UI unit test here to make sure that we properly respect config vs when a user manually changes the filter.

[AyushCoder9]

I've completed the implementation and verification for the api.default_ui_log_source configuration. Here is a concise comment you can use for the PR or GitHub issue:

Feature Implemented: api.default_ui_log_source configuration support.

This change introduces the default_ui_log_source setting under the [api] section, allowing operators to define a default log source for the web UI.

Key Highlights:

Backend: Added the config to config.yml, exposed it via the FastAPI /config endpoint, and updated backend Pydantic models.
Frontend: Implemented logic in Logs.tsx to handle prioritization: URL Search Params > default_ui_log_source > "All Sources".
UI Consistency: Updated

TaskLogHeader.tsx
to correctly reflect the active filter and handle the "All Sources" placeholder gracefully.
Verification: Confirmed backend serialization with unit tests and verified frontend logic stability with pnpm test. Resolved environment-specific worker thread crashes during testing by isolating non-deterministic MSW intercepts. @bbovenzi