fix: remove hardcoded localhost fallbacks, require explicit config

Critical fix for Docker deployment where AI features were trying to connect
to localhost:11434 instead of using configured provider (Ollama Docker service
or OpenAI).

Problems fixed:
1. Reformulation (clarify/shorten/improve) failing with ECONNREFUSED 127.0.0.1:11434
2. Auto-labels failing with same error
3. Notebook summaries failing
4. Could not switch from Ollama to OpenAI in admin

Root cause:
- Code had hardcoded fallback to 'http://localhost:11434' in multiple places
- .env.docker file not created on server (gitignore'd)
- No validation that required environment variables were set

Changes:

1. lib/ai/factory.ts:
   - Remove hardcoded 'http://localhost:11434' fallback
   - Only use localhost for local development (NODE_ENV !== 'production')
   - Throw error if OLLAMA_BASE_URL not set in production

2. lib/ai/providers/ollama.ts:
   - Remove default parameter 'http://localhost:11434' from constructor
   - Require baseUrl to be explicitly passed
   - Throw error if baseUrl is missing

3. lib/ai/services/paragraph-refactor.service.ts:
   - Remove 'http://localhost:11434' fallback (2 locations)
   - Require OLLAMA_BASE_URL to be set
   - Throw clear error if not configured

4. app/(main)/admin/settings/admin-settings-form.tsx:
   - Add debug info showing current provider state
   - Display database config value for transparency
   - Help troubleshoot provider selection issues

5. DOCKER-SETUP.md:
   - Complete guide for Docker configuration
   - Instructions for .env.docker setup
   - Examples for Ollama Docker, OpenAI, and external Ollama
   - Troubleshooting common issues

Usage:
On server, create .env.docker with proper provider configuration:
- Ollama in Docker: OLLAMA_BASE_URL="http://ollama:11434"
- OpenAI: OPENAI_API_KEY="sk-..."
- External Ollama: OLLAMA_BASE_URL="http://SERVER_IP:11434"

Then in admin interface, users can independently configure:
- Tags Provider (for auto-labels, AI features)
- Embeddings Provider (for semantic search)

Result:
✓ Clear errors if Ollama not configured
✓ Can switch to OpenAI freely in admin
✓ No more hardcoded localhost in production
✓ Proper separation between local dev and Docker production

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

keep-notes/app/(main)/admin/settings/admin-settings-form.tsx

@@ -300,7 +300,12 @@ export function AdminSettingsForm({ config }: { config: Record<string, string> }
               <p className="text-xs text-muted-foreground">AI provider for semantic search embeddings. Recommended: OpenAI (best quality).</p>
 
               <div className="space-y-2">
-                <Label htmlFor="AI_PROVIDER_EMBEDDING">Provider</Label>
+                <Label htmlFor="AI_PROVIDER_EMBEDDING">
+                  Provider
+                  <span className="ml-2 text-xs text-muted-foreground">
+                    (Current: {embeddingsProvider})
+                  </span>
+                </Label>
                 <select
                   id="AI_PROVIDER_EMBEDDING"
                   name="AI_PROVIDER_EMBEDDING"
@@ -312,6 +317,9 @@ export function AdminSettingsForm({ config }: { config: Record<string, string> }
                   <option value="openai">🤖 OpenAI (text-embedding-4)</option>
                   <option value="custom">🔧 Custom OpenAI-Compatible</option>
                 </select>
+                <p className="text-xs text-muted-foreground">
+                  Config value: {config.AI_PROVIDER_EMBEDDING || 'Not set (defaults to ollama)'}
+                </p>
               </div>
 
               {/* Ollama Embeddings Config */}