Fix month-change MetricasDiarias corruption and -0€ display in Slack report

- run.py: skip metricas update when campaign has no prior-month
  GACampaignMes record instead of silently writing into the new month
- slack_reporter.py: round before formatting so small negative margins
  don't render as "-0€"

run.py

@@ -400,6 +400,8 @@ def run():
         if cambio_mes:
             # Ayer pertenece al mes anterior: redirigir escritura al GACampaignMes correcto
             prev_map = at.get_gcm_id_map_for_month(ayer.month, ayer.year)
+            redirected = []
+            omitidos = []
             for u in metricas_updates:
                 gid = next(
                     (item["campaign"]["google_campaign_id"]
@@ -408,6 +410,13 @@ def run():
                 )
                 if gid and gid in prev_map:
                     u["airtable_id"] = prev_map[gid]
+                    redirected.append(u)
+                else:
+                    omitidos.append(gid)
+            metricas_updates = redirected
+            if omitidos:
+                print(f"  ⚠️  {len(omitidos)} campañas sin GACampaignMes en {ayer.month}/{ayer.year}, "
+                      f"MetricasDiarias del día anterior omitido para no contaminar el mes nuevo: {omitidos}")
         at.batch_update_metricas_diarias(metricas_updates)
         print("  ✓ MetricasDiarias actualizado.")
 

slack_reporter.py

@@ -73,8 +73,9 @@ def _trunc(text: str, limit: int = 2950) -> str:
 
 
 def _fmt_eur(v: float) -> str:
-    sign = "+" if v > 0 else ""
-    return f"{sign}{v:,.0f}€".replace(",", ".")
+    v_int = round(v)
+    sign = "+" if v_int > 0 else ""
+    return f"{sign}{v_int:,.0f}€".replace(",", ".")
 
 
 def _curso(name: str, max_len: int = 40) -> str:
@@ -196,7 +197,8 @@ def build_and_send(collected: list, dry_run: bool, prev_month_metricas: dict = N
         return f"{v:,.0f}€".replace(",", ".")
 
     def _marg(v: float) -> str:
-        return ("+" if v >= 0 else "") + f"{v:,.0f}€".replace(",", ".")
+        v_int = round(v)
+        return ("+" if v_int >= 0 else "") + f"{v_int:,.0f}€".replace(",", ".")
 
     def _pct(v: float) -> str:
         return ("+" if v >= 0 else "") + f"{v:.1f}%"