feat(ui) : apply pastel project colors on project cards and calendar blocks

- Project cards (/projects): 16px radius, pastel background, no border
- Time tracking calendar blocks: pastel opaque background, project color text

Ticket: LST-29

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/pages/projects/index.vue

@@ -29,8 +29,9 @@
             <div
                 v-for="project in projects"
                 :key="project.id"
-                class="cursor-pointer rounded-[6px] border border-neutral-200 bg-tertiary-500 p-4 shadow-sm transition hover:shadow-md"
+                class="cursor-pointer p-4 shadow-sm transition hover:shadow-md"
                 :class="{ 'opacity-60': project.archived }"
+                :style="projectCardStyle(project.color)"
                 @click="navigateTo(`/projects/${project.id}`)"
             >
                 <div class="flex items-center justify-between">
@@ -80,6 +81,17 @@ import { useClientService } from '~/services/clients'
 
 useHead({ title: 'Projets' })
 
+function projectCardStyle(color: string | null) {
+    const hex = (color || '#222783').replace('#', '')
+    const r = parseInt(hex.substring(0, 2), 16)
+    const g = parseInt(hex.substring(2, 4), 16)
+    const b = parseInt(hex.substring(4, 6), 16)
+    return {
+        borderRadius: '16px',
+        backgroundColor: `rgba(${r}, ${g}, ${b}, 0.08)`,
+    }
+}
+
 const projectService = useProjectService()
 const clientService = useClientService()