chore: enable @typescript-eslint/no-unsafe-* rules

[aminamos]

Summary:

Resolves #161.
Enables @typescript-eslint/no-unsafe-assignment, no-unsafe-member-access, and no-unsafe-call with explicit type safety across feed services.

Expected behavior:

Full type coverage without unchecked any-casts in core services.

Testing tips:

1. Checkout feat/161-enable-no-unsafe-rules.
2. Run yarn lint.

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• Run the unit tests with yarn test to make sure you didn't break anything
• Add or update any needed documentation to the repo
• Format the title like "feat: [new feature short description]". Title must follow the Conventional Commit Specification(https://www.conventionalcommits.org/en/v1.0.0/).
• Linked all relevant issues
• Include screenshot(s) showing how this pull request works and fixes the issue(s)

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