Add GitHub Actions CI + Windows notes on the developer docs

GitHub had no CI, so naming/tests/build were unenforced on the public
mirror. Add .github/workflows/ci.yml mirroring the internal pipeline:
backend pytest, the naming gate, frontend vitest+build, and the
migrations-mysql job that proves a fresh flask db upgrade + every
plugin chain on utf8mb4 MySQL 8 is idempotent. Flip the dev-setup CI
note to reflect it. Add an identical Windows/VS Code convention note to
the four developer docs (venv\Scripts vs venv/bin, $env: vs export,
pointer to DEVELOPMENT-SETUP).

.github/workflows/ci.yml

@@ -0,0 +1,109 @@
+# CI for shopdb-flask on GitHub Actions.
+#
+# Mirrors the internal gitea pipeline. Four jobs on push + pull_request:
+#   backend          - pytest (SQLite via TestingConfig, no DB service needed)
+#   naming           - the CONTRIBUTING.md naming/style gate
+#   frontend         - vitest + Vue build
+#   migrations-mysql - the REAL multi-site deploy path: fresh flask db upgrade
+#                      + every plugin's chain on utf8mb4 MySQL 8, idempotent on
+#                      a second run. The pytest suite only exercises SQLite
+#                      create_all(), so this is what catches an Alembic
+#                      regression on MySQL before it ships.
+
+name: CI
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  backend:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.12'
+          cache: pip
+      - run: pip install -r requirements.txt
+      - run: python -m pytest -q
+
+  naming:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - run: bash scripts/check-naming-and-style.sh
+
+  frontend:
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: frontend
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+          cache: npm
+          cache-dependency-path: frontend/package-lock.json
+      - run: npm ci
+      - run: npx vitest run
+      - run: npm run build
+
+  migrations-mysql:
+    runs-on: ubuntu-latest
+    services:
+      mysql:
+        image: mysql:8.0
+        env:
+          MYSQL_ROOT_PASSWORD: root
+          MYSQL_DATABASE: shopdb_ci
+        ports:
+          - 3306:3306
+        options: >-
+          --health-cmd="mysqladmin ping -h localhost -uroot -proot"
+          --health-interval=5s --health-timeout=5s --health-retries=20
+    env:
+      FLASK_APP: shopdb
+      DATABASE_URL: mysql+pymysql://root:root@127.0.0.1:3306/shopdb_ci?charset=utf8mb4
+      SECRET_KEY: ci-secret
+      JWT_SECRET_KEY: ci-jwt-secret
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.12'
+          cache: pip
+      - run: pip install -r requirements.txt
+      - name: Force utf8mb4 on the CI database
+        run: |
+          mysql -h 127.0.0.1 -uroot -proot -e \
+            "ALTER DATABASE shopdb_ci CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;"
+      - name: Fresh core upgrade from empty
+        run: flask db upgrade
+      - name: Install every bundled plugin (runs its chain)
+        run: |
+          for p in computers employees geenforce knowledgebase machines \
+                   measuringtools network notifications printedparts printers \
+                   slides usb warranty; do
+            flask plugin install "$p"
+          done
+          flask plugin upgrade-all
+      - name: Assert schema built + utf8mb4
+        run: |
+          python - <<'PY'
+          from shopdb import create_app
+          from shopdb.extensions import db
+          from sqlalchemy import text
+          app = create_app()
+          with app.app_context():
+              tables = db.inspect(db.engine).get_table_names()
+              assert len(tables) >= 70, f'only {len(tables)} tables built'
+              row = db.session.execute(text(
+                  "SELECT default_character_set_name FROM information_schema.schemata "
+                  "WHERE schema_name = 'shopdb_ci'")).first()
+              assert row[0] == 'utf8mb4', f'charset is {row[0]}, not utf8mb4'
+              print(f'OK: {len(tables)} tables, charset {row[0]}')
+          PY
+      - name: Second core upgrade must be a clean no-op
+        run: flask db upgrade