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/terceros.py

@@ -79,8 +79,12 @@ async def preview_query(
     if not ok:
         return JSONResponse({"success": False, "message": f"Error Firebird: {msg}"})
 
+    if ":doc_num" in q["query_text"] and not doc_num:
+        fb.disconnect()
+        return JSONResponse({"success": False, "message": "Ingresa el número de documento para buscar el paciente"})
+
     params = {}
-    if ":doc_num" in q["query_text"] and doc_num:
+    if ":doc_num" in q["query_text"]:
         params["doc_num"] = doc_num
     if ":fecha_ini" in q["query_text"]:
         params["fecha_ini"] = "1900-01-01"
@@ -124,9 +128,13 @@ async def send_terceros(
     if not ok:
         return JSONResponse({"success": False, "message": f"Error Firebird: {msg}"})
 
+    if ":doc_num" in q["query_text"] and not doc_num:
+        fb.disconnect()
+        return JSONResponse({"success": False, "message": "Ingresa el número de documento"})
+
     params = {}
     if ":doc_num" in q["query_text"]:
-        params["doc_num"] = doc_num or configs.get("doc_num_default", "")
+        params["doc_num"] = doc_num
 
     success, error, rows = fb.execute_query(q["query_text"], params if params else None)
     fb.disconnect()