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)/info/index.tsx

@@ -3,12 +3,13 @@ import { Ionicons } from '@expo/vector-icons';
 import { useRouter } from 'expo-router';
 import { useFeeds } from '@/hooks/useFeeds';
 import { Colors } from '@/lib/colors';
+import type { Feed } from '@/types';
 
 export default function InfoListScreen() {
   const { data: feeds, isLoading } = useFeeds();
   const router = useRouter();
 
-  const renderItem = ({ item }: { item: any }) => (
+  const renderItem = ({ item }: { item: Feed }) => (
     <TouchableOpacity
       style={styles.card}
       onPress={() => router.push(`/(tabs)/info/${item.slug}`)}