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.

postcss.config.js

@@ -1,6 +1,5 @@
 export default {
   plugins: {
-    tailwindcss: {},
     autoprefixer: {},
     'postcss-import': {},
   },