Docs/update readme and screenshots

[VishakBaddur]

Description

Updates the README against the project's actual current state, swaps in current screenshots, and removes a third pocket of legacy Pinecone-era code that was still sitting inside api-service/ after the first two cleanup passes. Also fixes two real gaps I found while verifying this: pytest/pytest-mock were never in requirements.txt, so the test suite had never actually run inside the Docker image, only in local dev environments. And DistilBERT was only loading at runtime over the network instead of being preloaded at build time like the embedding model already was, which meant sentiment analysis would silently fall back to a default in any environment without reliable outbound access at boot.

Related Issue

#244

Motivation and Context

Docs and legacy code were both stale ahead of final submission. #241 (dashboard/Ask AI) and #236 (sources page) had shipped since the README was last touched, and there was still unused pre-restructure code (cybernews/, a second db_update/) sitting in api-service/ that nothing imports.

How Has This Been Tested?

Ran the full suite inside the actual Docker container, not just locally - docker compose up -d --build && docker compose exec api-service python -m pytest. 148 passed. Also manually verified every factual claim in the README against the current code (ingestion source loading, notification behavior, env vars) rather than carrying forward old wording.

Screenshots (if appropriate):

Old screenshots replaced with current dashboard, chat, sources, and landing pages - see the diff for assets/.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.