fix: unify dialog layout and fix content padding issues

- Fix negative margin overflow in all dialog content areas
- Standardize dialog structure with flex-col layout
- Add consistent py-4 spacing to all content areas
- Ensure proper spacing between header, content, and footer

Affected components:
- AddProviderDialog, EditProviderDialog
- McpFormModal, McpPanel
- UsageScriptModal
- SettingsDialog

All dialogs now follow unified layout pattern:
- DialogContent: flex flex-col max-h-[90vh]
- Content area: flex-1 overflow-y-auto px-6 py-4
- No negative margins that cause content overflow

src/components/providers/forms/ClaudeFormFields.tsx

@@ -41,7 +41,7 @@ interface ClaudeFormFieldsProps {
   claudeSmallFastModel: string;
   onModelChange: (
     field: "ANTHROPIC_MODEL" | "ANTHROPIC_SMALL_FAST_MODEL",
-    value: string
+    value: string,
   ) => void;
 
   // Kimi Model Selector
@@ -49,7 +49,7 @@ interface ClaudeFormFieldsProps {
   kimiAnthropicSmallFastModel: string;
   onKimiModelChange: (
     field: "ANTHROPIC_MODEL" | "ANTHROPIC_SMALL_FAST_MODEL",
-    value: string
+    value: string,
   ) => void;
 
   // Speed Test Endpoints