feat(ui): add Ollama logo and make API key optional

- Add Ollama SVG logo to ui/public/icons/
- Add icon property to both ollama and ollama-cloud presets
- Make API key field optional for local Ollama (show input with hint)
- Update placeholder: "Optional - only if auth is enabled"
- Allows power users with Ollama auth configured to provide key

ui/src/lib/provider-presets.ts

@@ -53,6 +53,7 @@ export const PROVIDER_PRESETS: ProviderPreset[] = [
     defaultProfileName: 'ollama',
     badge: 'Local',
     featured: true,
+    icon: '/icons/ollama.svg',
     defaultModel: 'qwen3-coder',
     requiresApiKey: false,
     apiKeyPlaceholder: '',
@@ -158,6 +159,7 @@ export const PROVIDER_PRESETS: ProviderPreset[] = [
     baseUrl: 'https://ollama.com',
     defaultProfileName: 'ollama-cloud',
     badge: 'Cloud',
+    icon: '/icons/ollama.svg',
     defaultModel: 'glm-4.7:cloud',
     requiresApiKey: true,
     apiKeyPlaceholder: 'YOUR_OLLAMA_CLOUD_API_KEY',