feat: add imageGeneration param

pages/docs/configuration/librechat_yaml/object_structure/file_config.mdx

@@ -4,11 +4,12 @@
 
 The `fileConfig` object allows you to configure file handling settings for the application, including size limits and MIME type restrictions. This section provides a detailed breakdown of the `fileConfig` object structure.
 
-There are 3 main fields under `fileConfig`:
+There are 4 main fields under `fileConfig`:
 
   - `endpoints`
   - `serverFileSizeLimit`
   - `avatarSizeLimit`
+  - `imageGeneration`
 
 **Notes:**
 
@@ -50,7 +51,9 @@ fileConfig:
         - "image/.*"
   serverFileSizeLimit: 1000
   avatarSizeLimit: 2
-
+  imageGeneration:
+    percentage: 100
+    px: 1024
 ```
 
 ## serverFileSizeLimit
@@ -66,7 +69,6 @@ fileConfig:
   serverFileSizeLimit: 1000
 ```
 
-
 ## avatarSizeLimit
 
 <OptionTable
@@ -80,6 +82,35 @@ fileConfig:
   avatarSizeLimit: 2
 ```
 
+## imageGeneration
+
+<OptionTable
+  options={[
+    ['imageGeneration', 'Object', 'Settings related to image generation output quality and dimensions.', 'Allows configuration of either output size as a percentage relative to some base size or as an explicit pixel dimension.'],
+  ]}
+/>
+
+`imageGeneration` supports the following parameters:
+
+- `percentage` (Integer)
+  - The output size of the generated image expressed as a percentage (e.g., `100` means 100% of base size).
+  - Use this to scale the output image relative to a default or original size.
+
+- `px` (Integer)
+  - Specifies the output image dimension in pixels (e.g., `1024`).
+  - Use this to explicitly set the output size of the generated image regardless of base size.
+
+You may set only one of these parameters (`percentage` or `px`), not both, depending on your use case
+
+Example configuration:
+
+```yaml filename="fileConfig / imageGeneration"
+fileConfig:
+  imageGeneration:
+    percentage: 100
+    px: 1024
+```
+
 ## endpoints
 
 <OptionTable