feat: prepare project for cozy-ui migration (#157)

* feat: prepare project for cozy-ui migration

Build Configuration
- Add Stylus support via @rsbuild/plugin-stylus
- Add SVGR support via @rsbuild/plugin-svgr
- Update rsbuild.config.ts with custom configuration
- Add historyApiFallback for SPA routing

ESLint Configuration
- Create .eslintrc.json with react-app configuration
- Remove eslintConfig from package.json

CSS to Stylus Migration
Convert all 5 CSS files to Stylus (.styl) format:
  - src/App.css to src/App.styl
  - src/index.css to src/index.styl
  - src/components/Calendar/Calendar.css to src/components/Calendar/Calendar.styl
  - src/components/Calendar/CustomCalendar.css to src/components/Calendar/CustomCalendar.styl
  - src/components/Menubar/Menubar.css to src/components/Menubar/Menubar.styl
- Update all imports from .css to .styl
- Preserve all styling rules and values

MUI Styling Cleanup
- Replace all MUI sx props with standard style props across 15+ components
- Convert MUI spacing units (mr: 2 to marginRight: 16px)
- Convert MUI shorthand props (p: 2 to padding: 16px, mb: 1 to marginBottom: 8px)
- Remove MUI-specific syntax (&.Mui-checked selectors)
- Maintain exact visual appearance

FullCalendar Fixes
- Comment out problematic CSS rule in CustomCalendar.styl
- Fix display issues with timegrid slot labels

Files Modified
- Config: rsbuild.config.ts, .eslintrc.json, package.json
- Styling: 5 CSS to Stylus conversions, 15+ component sx to style updates
- Components: All components using MUI sx props updated

Development Workflow
- Continue using existing development commands
- Stylus files are now the source of truth for styling
- MUI components work with standard style props
- ESLint uses familiar react-app rules

Dependencies Added
- @rsbuild/plugin-stylus
- @rsbuild/plugin-svgr

src/components/Event/EventRepeat.tsx

@@ -98,7 +98,7 @@ export default function RepeatEvent({
                 })
               }
               size="small"
-              sx={{ width: 80 }}
+              style={{ width: 80 }}
             />
             <Typography>
               {
@@ -136,7 +136,7 @@ export default function RepeatEvent({
 
           {/* End options */}
           <Box>
-            <Typography variant="body2" gutterBottom sx={{ mt: 2 }}>
+            <Typography variant="body2" gutterBottom style={{ marginTop: 16 }}>
               End:
             </Typography>
             <RadioGroup
@@ -187,7 +187,7 @@ export default function RepeatEvent({
                           occurrences: Number(e.target.value),
                         })
                       }
-                      sx={{ width: 100 }}
+                      style={{ width: 100 }}
                       inputProps={{ min: 1 }}
                       disabled={endOption !== "after"}
                     />