chore: durcit la configuration pour la production

- mobile: externalise l'URL d'API via EXPO_PUBLIC_API_URL (repli localhost en dev)
- backend: .env.example adapté au projet (PostgreSQL, JWT, FRONTEND_URL, Redis)
- frontend/mobile: ajoute .env.example (+ exception gitignore front)
- mobile: supprime les 4 `any` (helper getApiError, type Feed, glyphMap Ionicons)
- backend: normalise le style PSR-12 via Pint (13 fichiers)

Tests backend 15/15, mobile tsc 0, Pint pass.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

mobile/app/(tabs)/profile.tsx

@@ -67,10 +67,10 @@ export default function ProfileScreen() {
   );
 }
 
-function MenuItem({ icon, label }: { icon: string; label: string }) {
+function MenuItem({ icon, label }: { icon: keyof typeof Ionicons.glyphMap; label: string }) {
   return (
     <TouchableOpacity style={styles.menuItem}>
-      <Ionicons name={icon as any} size={20} color={Colors.gray[600]} />
+      <Ionicons name={icon} size={20} color={Colors.gray[600]} />
       <Text style={styles.menuLabel}>{label}</Text>
       <Ionicons name="chevron-forward" size={18} color={Colors.gray[300]} />
     </TouchableOpacity>