feat: add reset buttons for heures/jours/doses stats, fix home button color

- StatsScreen: SectionResetBtn for heures d'affluence, jours d'affluence, doses populaires
- api_admin.ts: extend StatSection and AdminStats with heures/jours/doses fields
- HomeScreen (mobile client): use colors.accent for Se connecter button

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

mobile/src/screens/HomeScreen.tsx

@@ -22,7 +22,7 @@ export default function HomeScreen({ navigation }: Props) {
                 </Text>
 
                 <TouchableOpacity
-                    style={styles.button}
+                    style={[styles.button, { backgroundColor: colors.accent }]}
                     onPress={() => navigation.navigate("login")}
                 >
                     <Text style={styles.buttonText}>Se connecter</Text>
@@ -58,7 +58,6 @@ const styles = StyleSheet.create({
         textAlign: "center",
     },
     button: {
-        backgroundColor: "#7c3aed",
         borderRadius: 8,
         paddingVertical: 12,
         paddingHorizontal: 24,