v2: empty sections fallback in email template

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

backend/src/services/email.rs

@@ -138,6 +138,10 @@ fn html_escape(s: &str) -> String {
 pub fn build_synthesis_html(week: &str, date: &str, sections: &[NewsSection]) -> String {
     let mut items_html = String::new();
 
+    if sections.is_empty() {
+        items_html.push_str("<p style=\"text-align:center;color:#6b7280;font-style:italic;padding:24px 0;\">Aucune section trouvee dans cette synthese.</p>");
+    }
+
     for section in sections {
         items_html.push_str(&format!(
             r#"<tr><td style="padding: 24px 0 8px 0;">
@@ -204,6 +208,10 @@ pub fn build_synthesis_text(week: &str, date: &str, sections: &[NewsSection]) ->
     text.push_str(&"=".repeat(50));
     text.push('\n');
 
+    if sections.is_empty() {
+        text.push_str("\nAucune section trouvee dans cette synthese.\n");
+    }
+
     for section in sections {
         text.push_str(&format!("\n{}\n", section.title.to_uppercase()));
         text.push_str(&"-".repeat(section.title.len()));
@@ -353,4 +361,16 @@ mod tests {
         assert!(text.contains("Generee le 2026-03-21"));
         assert!(text.contains("Genere par AI Weekly Synth"));
     }
+
+    #[test]
+    fn test_synthesis_html_empty_sections_shows_fallback() {
+        let html = build_synthesis_html("2026-W12", "21 mars 2026", &[]);
+        assert!(html.contains("Aucune section trouvee"));
+    }
+
+    #[test]
+    fn test_synthesis_text_empty_sections_shows_fallback() {
+        let text = build_synthesis_text("2026-W12", "21 mars 2026", &[]);
+        assert!(text.contains("Aucune section trouvee"));
+    }
 }