Fix param validation errors and add TNS config section

- terceros/transaccion: return clear error when required params (doc_num, num_factura) are missing instead of passing empty dict to Firebird causing Column unknown error
- transaccion: remove prefijo from 'por factura' query; parse num_factura as int when digit
- automation: add /preview endpoint to show patient/reception counts before sending; update UI with preview step and disabled run button until preview loads
- config: add TNS credentials section (tns_empresa, tns_usuario, tns_password, api_sucursal) with test-connection button
- config: add POST /config/test-tns endpoint

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

app/routes/automation.py

@@ -76,6 +76,57 @@ async def automation_page(request: Request, user: dict = Depends(get_current_use
     })
 
 
+@router.post("/preview")
+async def preview_automation(
+    request: Request,
+    user: dict = Depends(get_current_user),
+    fecha: str = Form(...),
+):
+    conn = get_connection()
+    configs = {row["key"]: row["value"] for row in conn.execute("SELECT * FROM config").fetchall()}
+    conn.close()
+
+    fb, fb_ok, fb_msg = get_firebird_from_config(configs)
+    if not fb_ok:
+        return JSONResponse({"success": False, "message": f"Error Firebird: {fb_msg}"})
+
+    fecha_ini = f"{fecha} 00:00:00"
+    fecha_fin = f"{fecha} 23:59:59"
+    params = {"fecha_ini": fecha_ini, "fecha_fin": fecha_fin}
+
+    ok1, err1, rows_pac = fb.execute_query(_SQL_PACIENTES, params)
+    if not ok1:
+        fb.disconnect()
+        return JSONResponse({"success": False, "message": f"Error BD pacientes: {err1}"})
+
+    ok2, err2, rows_rda = fb.execute_query(_SQL_RDA, params)
+    fb.disconnect()
+    if not ok2:
+        return JSONResponse({"success": False, "message": f"Error BD RDA: {err2}"})
+
+    grupos = agrupar_por_recepcion(rows_rda)
+    total_examenes = sum(len(v) for v in grupos.values())
+
+    pacientes_preview = [
+        {
+            "doc": str(p.get("DOCIDENT", "")),
+            "nombre": f"{p.get('NOMBRES', '')} {p.get('APELLIDOS', '')}".strip(),
+            "tipo": str(p.get("TIPOIDENT", "")),
+        }
+        for p in rows_pac[:10]
+    ]
+
+    return JSONResponse({
+        "success": True,
+        "fecha": fecha,
+        "pacientes": len(rows_pac),
+        "recepciones": len(grupos),
+        "examenes": total_examenes,
+        "pacientes_preview": pacientes_preview,
+        "hay_mas": len(rows_pac) > 10,
+    })
+
+
 @router.post("/run")
 async def run_automation(
     request: Request,