refactor: consolidate provider form components

This commit completes Stage 2.5-2.6 of the refactoring plan by:

- Consolidating 8 provider form files (1941+ lines) into a single
  unified ProviderForm component (353 lines), reducing code by ~82%
- Implementing modern form management with react-hook-form and zod
- Adding preset provider categorization with grouped select UI
- Supporting dual-mode operation for both Claude and Codex configs
- Removing redundant subcomponents:
  - ApiKeyInput.tsx (72 lines)
  - ClaudeConfigEditor.tsx (205 lines)
  - CodexConfigEditor.tsx (667 lines)
  - EndpointSpeedTest.tsx (636 lines)
  - KimiModelSelector.tsx (195 lines)
  - PresetSelector.tsx (119 lines)

Key improvements:
- Type-safe form values with ProviderFormValues extension
- Automatic template value application for presets
- Better internationalization coverage
- Cleaner separation of concerns
- Enhanced UX with categorized preset groups

Updates AddProviderDialog and EditProviderDialog to pass appType prop
and handle preset category metadata.

src/components/providers/AddProviderDialog.tsx

@@ -40,7 +40,7 @@ export function AddProviderDialog({
         name: values.name.trim(),
         websiteUrl: values.websiteUrl?.trim() || undefined,
         settingsConfig: parsedConfig,
-        meta: {},
+        ...(values.presetCategory ? { category: values.presetCategory } : {}),
       };
 
       await onSubmit(providerData);
@@ -67,6 +67,7 @@ export function AddProviderDialog({
         </DialogHeader>
 
         <ProviderForm
+          appType={appType}
           submitLabel={t("common.add", { defaultValue: "添加" })}
           onSubmit={handleSubmit}
           onCancel={() => onOpenChange(false)}