fix(translate): increase max_tokens 4096→8192 for DeepSeek multi-language output

finish_reason=length from DeepSeek v4 Flash — model runs out of
output tokens due to reasoning_content (CoT) + multi-language (4 langs).
8192 tokens ensures complete JSON response for preview and execution.

backend/src/plugins/translate/executor.py

@@ -946,7 +946,7 @@ class TranslationExecutor:
                     {"role": "user", "content": prompt},
                 ],
                 "temperature": 0.1,
-                "max_tokens": 4096,
+                "max_tokens": 8192,
             }
             # Structured output (response_format) only for native OpenAI — upstream providers routed via
             # Kilo/OpenRouter may not support it (e.g. StepFun returns "structured_outputs is not supported")

backend/src/plugins/translate/preview.py

@@ -952,7 +952,7 @@ class TranslationPreview:
                     {"role": "user", "content": prompt},
                 ],
                 "temperature": 0.1,
-                "max_tokens": 4096,
+                "max_tokens": 8192,
             }
             # Structured output (response_format) only for native OpenAI — upstream providers routed via
             # Kilo/OpenRouter may not support it (e.g. StepFun returns "structured_outputs is not supported")