Setup CI Workflows for the frontend and backend

[TKDPenguin]

Overview

Provide a brief summary of the changes you made and files touched.

• Implemented CI setup across the project
  • Backend
    • Migrated dependencies from requirements.txt to pyproject.toml and uv.lock
    • Updated Dockerfile to use pinned uv and uv sync --frozen
    • Added PostgreSQL test-db, healthcheck, and optional .env handling in docker-compose.yml
    • Updated BackendCI.yml triggers and database readiness checks.
    • Removed backend/requirements.txt.
  • Frontend
    • Added ESLint, TypeScript checking, Vitest, coverage tooling, and a smoke test.
    • Updated package.json and package-lock.json.
    • Added eslint.config.js, tsconfig.json, vitest.config.js, App.test.jsx, and test-setup.js.
    • Added coverage/ to .gitignore.

[henrybednarz]

lgtm