feat(linux): bundle Python CLI and fix Electron packaged build

- contrib/linux/Dockerfile: add libpython3.11 + PyInstaller to build
  standalone cli binary; fix venv isolation via .dockerignore
- frontend/electron/main.cjs: use bundled cli binary in prod via
  process.resourcesPath, fallback to venv/python3 in dev
- frontend/package.json: add extraResources for cli binary,
  set output dir to release/
- frontend/vite.config.js: set base './' for file:// protocol in prod
- .dockerignore: exclude venv/, node_modules/, dist/, .git/
- .gitignore: ignore release/ output directories

contrib/linux/Dockerfile

@@ -0,0 +1,31 @@
+FROM node:22.14.0-bookworm
+
+# System dependencies
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    python3 python3-pip python3-venv libpython3.11 \
+    binutils \
+    && rm -rf /var/lib/apt/lists/*
+
+WORKDIR /build
+
+# Copy repo
+COPY . .
+
+# Python venv + dependencies
+RUN python3 -m venv venv && \
+    venv/bin/pip install --no-cache-dir -r requirements.txt
+
+# Compile Python CLI into a standalone binary
+RUN venv/bin/pip install --no-cache-dir pyinstaller && \
+    venv/bin/pyinstaller --onefile --name cli src/cli.py && \
+    mkdir -p frontend/resources && \
+    cp dist/cli frontend/resources/cli
+
+# JS dependencies + electron-builder
+RUN cd frontend && npm ci && npm install --no-save electron-builder
+
+# Build
+RUN cd frontend && npx vite build && npx electron-builder --linux AppImage --publish never
+
+# Export AppImage
+CMD cp frontend/release/*.AppImage /out/