feat : migrate filter/form UI to @malio/layer-ui + fix hours/calendar contract scoping

- Add @malio/layer-ui as Nuxt layer (extends in nuxt.config.ts)
- Migrate site/employee/contract filters to MalioSelectCheckbox / MalioInputText / MalioSelect on employees, calendar and hours screens
- Migrate absence drawer selects + submit button to Malio (MalioSelect + MalioButton)
- Migrate calendar "Ajouter une absence" / "Imprimer" actions to MalioButton
- Drop now-unused EmployeeNameFilterInput and SiteFilterSelector components
- Hours day view: resolve contract nature at selected date (WorkHourDayContext.contractNature) instead of employee.currentContractNature (today-based); fixes interim contracts showing as CDI when mission ended
- Calendar: hide employees whose contract periods do not intersect the displayed month
- Layout: scrollbar-gutter:stable on <main> to avoid horizontal shift when dropdowns open
- Update functional-rules.md, in-app documentation, CLAUDE.md to match

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

tests/State/WorkHourDayContextProviderTest.php

@@ -10,6 +10,7 @@ use App\Entity\AbsenceType;
 use App\Entity\Contract;
 use App\Entity\Employee;
 use App\Entity\User;
+use App\Enum\ContractNature;
 use App\Enum\HalfDay;
 use App\Repository\Contract\AbsenceReadRepositoryInterface;
 use App\Repository\Contract\EmployeeScopedRepositoryInterface;
@@ -176,6 +177,10 @@ final class WorkHourDayContextProviderTest extends TestCase
             ->method('resolveForEmployeeAndDate')
             ->willReturnCallback(static fn (Employee $employee): ?Contract => $employee->getContract())
         ;
+        $resolver
+            ->method('resolveNatureForEmployeeAndDate')
+            ->willReturn(ContractNature::CDI)
+        ;
 
         return $resolver;
     }