feat: dark-tech UI redesign + markdown patch cards

Redesign the frontend with a dark-tech theme: add Tailwind + PostCSS,
design tokens, and shadcn-style primitives (Button/Card/Input/Dialog/
DropdownMenu/Tabs/ScrollArea/etc.); restyle the app shell, navigation,
sidebar tree, content view, markdown rendering, editors, modals and
settings panels. Behavior/props unchanged; Font Awesome replaced with
lucide-react.

Add the patch cards feature UI: patch-queries hooks and a PatchCards
component rendered below the markdown body, with an Add Patch button
and create/edit dialog.

Fix tree expandability: folders with an index page now expand on name
click (and navigate), and the chevron+folder icon is one larger toggle.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

package.json

@@ -12,10 +12,20 @@
   "author": "",
   "license": "ISC",
   "dependencies": {
+    "@radix-ui/react-dialog": "^1.1.4",
+    "@radix-ui/react-dropdown-menu": "^2.1.4",
+    "@radix-ui/react-scroll-area": "^1.2.2",
+    "@radix-ui/react-separator": "^1.1.1",
+    "@radix-ui/react-slot": "^1.1.1",
+    "@radix-ui/react-tabs": "^1.1.2",
+    "@radix-ui/react-tooltip": "^1.1.6",
     "@reduxjs/toolkit": "^2.7.0",
     "@tanstack/react-query": "^5.75.5",
     "@tanstack/react-query-devtools": "^5.75.5",
     "assert": "^2.1.0",
+    "class-variance-authority": "^0.7.1",
+    "clsx": "^2.1.1",
+    "lucide-react": "^0.469.0",
     "axios": "^1.7.9",
     "bulma": "^1.0.2",
     "katex": "^0.16.11",
@@ -35,6 +45,7 @@
     "rehype-sanitize": "^6.0.0",
     "remark-gfm": "^4.0.0",
     "remark-math": "^6.0.0",
+    "tailwind-merge": "^2.6.0",
     "util": "^0.12.5"
   },
   "devDependencies": {
@@ -44,10 +55,13 @@
     "@testing-library/jest-dom": "^6.6.3",
     "@testing-library/react": "^16.1.0",
     "@testing-library/user-event": "^14.5.2",
+    "autoprefixer": "^10.4.20",
     "axios-mock-adapter": "^2.1.0",
     "babel-jest": "^29.7.0",
     "babel-loader": "^9.2.1",
     "css-loader": "^7.1.2",
+    "postcss": "^8.4.49",
+    "postcss-loader": "^8.1.1",
     "dotenv-webpack": "^8.1.0",
     "html-webpack-plugin": "^5.6.3",
     "identity-obj-proxy": "^3.0.0",
@@ -57,6 +71,7 @@
     "sass": "^1.81.0",
     "sass-loader": "^16.0.3",
     "style-loader": "^4.0.0",
+    "tailwindcss": "^3.4.17",
     "webpack": "^5.96.1",
     "webpack-cli": "^5.1.4",
     "webpack-dev-server": "^5.1.0"