feat(providers): add provider categorization system

- Add ProviderCategory type with official, cn_official, aggregator, third_party, and custom categories
- Update Provider interface and Rust struct to include optional category field
- Enhance ProviderForm to automatically sync category when selecting presets
- Improve PresetSelector to show category-based styling and hints
- Add category classification to all provider presets
- Support differentiated interactions (e.g., hide API key input for official providers)
- Maintain backward compatibility with existing configurations

src-tauri/src/provider.rs

@@ -14,6 +14,8 @@ pub struct Provider {
     #[serde(skip_serializing_if = "Option::is_none")]
     #[serde(rename = "websiteUrl")]
     pub website_url: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub category: Option<String>,
 }
 
 impl Provider {
@@ -29,6 +31,7 @@ impl Provider {
             name,
             settings_config,
             website_url,
+            category: None,
         }
     }
 }