Feat: add Gemini 3 Pro preview (#11361)

### What problem does this PR solve?

Add Gemini 3 Pro preview.

Change `GenerativeModel` to `genai`.

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

conf/llm_factories.json

@@ -1429,6 +1429,13 @@
             "status": "1",
             "rank": "980",
             "llm": [
+                {
+                    "llm_name": "gemini-3-pro-preview",
+                    "tags": "LLM,CHAT,1M,IMAGE2TEXT",
+                    "max_tokens": 1048576,
+                    "model_type": "image2text",
+                    "is_tools": true
+                },
                 {
                     "llm_name": "gemini-2.5-flash",
                     "tags": "LLM,CHAT,1024K,IMAGE2TEXT",
@@ -5474,4 +5481,4 @@
             ]
         }
     ]
-}
+}