feat(theme): apply new color palette and polish UI

- Add theme variables and restyle popup/options using Primary 3 as background and Primary 2 as surfaces; accents use Primary 1.\n- Move Save to a footer section on the options page; add responsive layout and button variants.\n- Update icon build defaults to use Primary 2 for add-on and Primary 1 for toolbar icons.\n- Add build-and-commit helper to run build, stage generated assets, commit, and optionally push.\n- Add npm scripts: build:commit and build:commit:push.

package.json

@@ -7,6 +7,8 @@
     "dev": "web-ext run --start-url https://archive.org --source-dir .",
     "build:icons": "node scripts/build-icons.js",
     "build": "npm run build:icons && web-ext build -o -a dist",
+    "build:commit": "node scripts/build-and-commit.js",
+    "build:commit:push": "PUSH=true node scripts/build-and-commit.js --push",
     "lint": "echo 'Add ESLint config to enable' && exit 0",
     "format": "echo 'Add Prettier config to enable' && exit 0",
     "test": "echo 'No tests yet' && exit 0",