chore: remove Tailwind CSS build pipeline; replace with tailwind-compat.css shim

244 utility classes across 8 files (timetable pages, Modal, CCShapesPanel).
Rather than blind inline conversion, replace @tailwind directives with a
self-contained 230-line CSS shim covering all classes actually used.
Build passes. Shim entries can be converted to --cc-* tokens incrementally.

package.json

@@ -84,7 +84,6 @@
     "postcss": "^8.4.38",
     "prettier": "^3.2.5",
     "react-refresh": "^0.14.2",
-    "tailwindcss": "^3.4.3",
     "typescript": "^5.2.2",
     "vite-plugin-pwa": "^0.21.1",
     "vitest": "^1.6.0"