✨ feat(frontend): barre de progression XP style RPG

Story 3.4 : Barre de progression globale (XP bar)
- ProgressBar.vue avec design RPG (bordure, graduations, glow)
- Tooltip au hover avec liste des sections visitées
- Animation fluide avec prefers-reduced-motion
- ProgressIcon.vue pour mobile (cercle SVG + drawer)
- Intégration dans AppHeader (visible si héros choisi)
- Traductions progress.* FR/EN

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/i18n/en.json

@@ -179,6 +179,17 @@
     "clickToSkip": "Click or press Space to skip",
     "bugAlt": "The Bug - Stage {stage}"
   },
+  "progress": {
+    "label": "Progress: {percent}%",
+    "title": "Portfolio exploration",
+    "sections": {
+      "projects": "Projects",
+      "skills": "Skills",
+      "testimonials": "Testimonials",
+      "journey": "Journey"
+    },
+    "summary": "{visited} visited, {remaining} to discover"
+  },
   "pages": {
     "projects": {
       "title": "Projects",