Add GitHub Actions CI for backend and frontend

[Copilot]

No CI existed to validate backend syntax or frontend build integrity on push/PR.

Changes

.github/workflows/ci.yml — two parallel jobs:

• Backend (Python 3.12): pip-cached install of backend/requirements.txt, py_compile validation of all .py files, optional pytest if tests directory is present
• Frontend (Node 20): node_modules cache keyed on package-lock.json + package.json, npm install, npm run build — fails job on build error
• Workflow-level permissions: contents: read to minimize GITHUB_TOKEN scope

README.md — CI status badge added to the header badge row.

jobs:
  backend:
    ...
    steps:
      - uses: actions/setup-python@v5
        with:
          python-version: "3.12"
          cache: "pip"
          cache-dependency-path: backend/requirements.txt

  frontend:
    ...
    steps:
      - uses: actions/cache@v4
        with:
          path: skydash/frontend/node_modules
          key: ${{ runner.os }}-node-${{ hashFiles('skydash/frontend/package-lock.json', 'skydash/frontend/package.json') }}

---

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[Copilot]

Pull request overview

This PR adds GitHub Actions CI/CD workflows to validate backend Python syntax and frontend build integrity on push and pull requests. The implementation addresses the "CI/CD Pipeline" item mentioned in the project's technical debt section (README.md:299).

Changes:

• Added .github/workflows/ci.yml with parallel backend (Python 3.12 syntax validation via py_compile, optional pytest) and frontend (Node 20 build verification) jobs
• Added CI status badge to README.md header

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
.github/workflows/ci.yml	New CI workflow with backend Python compilation checks and frontend build validation, includes caching for pip and node_modules
README.md	Added CI status badge linking to workflow runs

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[Copilot]

The cache key includes 'package-lock.json', but this file does not exist in the repository. The cache key will fail to generate a hash for the missing file. Consider either generating a package-lock.json file by running 'npm install' locally and committing it, or update the cache key to only use 'package.json'. Using package-lock.json is recommended for reproducible builds.

Suggested change

	key: ${{ runner.os }}-node-${{ hashFiles('skydash/frontend/package-lock.json', 'skydash/frontend/package.json') }}
	key: ${{ runner.os }}-node-${{ hashFiles('skydash/frontend/package.json') }}

[Copilot]

The setup-node action (v4) has built-in caching support when you specify the 'cache' parameter. This manual cache action is redundant and can be removed. Instead, add 'cache: npm' to the setup-node step and specify 'cache-dependency-path: skydash/frontend/package-lock.json' (or just package.json if package-lock.json doesn't exist). This simplifies the workflow and follows GitHub Actions best practices.

Suggested change

	- name: Cache node_modules
	uses: actions/cache@v4
	with:
	path: skydash/frontend/node_modules
	key: ${{ runner.os }}-node-${{ hashFiles('skydash/frontend/package-lock.json', 'skydash/frontend/package.json') }}
	restore-keys: |
	${{ runner.os }}-node-
	cache: npm
	cache-dependency-path: skydash/frontend/package-lock.json