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

frontend/package.json

@@ -1,5 +1,5 @@
 {
-  "name": "wallet-generator",
+  "name": "wallet-gen",
   "private": true,
   "version": "1.0.0",
   "type": "module",
@@ -12,10 +12,16 @@
     "dist":    "vite build && electron-builder"
   },
   "build": {
-    "appId": "com.walletgenerator.app",
-    "productName": "Wallet Generator",
+    "appId": "com.walletgen.app",
+    "productName": "wallet-gen",
     "icon": "public/icons/icon.png",
     "files": ["dist/**", "electron/**"],
+    "extraResources": [
+      { "from": "resources/cli", "to": "cli" }
+    ],
+    "directories": {
+      "output": "release"
+    },
     "linux": {
       "target": "AppImage",
       "category": "Finance"