feat: AI provider testing page + multi-provider support + UX design spec

- Add AI Provider Testing page (/admin/ai-test) with Tags and Embeddings tests
- Add new AI providers: CustomOpenAI, DeepSeek, OpenRouter
- Add API routes for AI config, models listing, and testing endpoints
- Add UX Design Specification document for Phase 1 MVP AI
- Add PRD Phase 1 MVP AI planning document
- Update admin settings and sidebar navigation
- Fix AI factory for multi-provider support

keep-notes/app/api/ai/config/route.ts

@@ -0,0 +1,27 @@
+import { NextRequest, NextResponse } from 'next/server'
+import { getSystemConfig } from '@/lib/config'
+
+export async function GET(request: NextRequest) {
+  try {
+    const config = await getSystemConfig()
+
+    return NextResponse.json({
+      AI_PROVIDER_TAGS: config.AI_PROVIDER_TAGS || 'ollama',
+      AI_MODEL_TAGS: config.AI_MODEL_TAGS || 'granite4:latest',
+      AI_PROVIDER_EMBEDDING: config.AI_PROVIDER_EMBEDDING || 'ollama',
+      AI_MODEL_EMBEDDING: config.AI_MODEL_EMBEDDING || 'embeddinggemma:latest',
+      OPENAI_API_KEY: config.OPENAI_API_KEY ? '***configured***' : '',
+      CUSTOM_OPENAI_API_KEY: config.CUSTOM_OPENAI_API_KEY ? '***configured***' : '',
+      CUSTOM_OPENAI_BASE_URL: config.CUSTOM_OPENAI_BASE_URL || '',
+      OLLAMA_BASE_URL: config.OLLAMA_BASE_URL || 'http://localhost:11434'
+    })
+  } catch (error: any) {
+    console.error('Error fetching AI config:', error)
+    return NextResponse.json(
+      {
+        error: error.message || 'Failed to fetch config'
+      },
+      { status: 500 }
+    )
+  }
+}