fix: remove Ollama default fallbacks in factory and Docker

ROOT CAUSE: The factory was defaulting to 'ollama' when no provider
was configured, and docker-compose.yml was always setting OLLAMA_BASE_URL
even when using OpenAI. This caused the app to try connecting to Ollama
even when OpenAI was configured in the admin.

CRITICAL CHANGES:
1. lib/ai/factory.ts - Removed 'ollama' default fallback
   - getTagsProvider() now throws error if AI_PROVIDER_TAGS not set
   - getEmbeddingsProvider() now throws error if AI_PROVIDER_EMBEDDING not set
   - Forces explicit configuration instead of silent fallback to Ollama

2. docker-compose.yml - Removed default OLLAMA_BASE_URL
   - Changed: OLLAMA_BASE_URL=${OLLAMA_BASE_URL:-http://ollama:11434}
   - To: OLLAMA_BASE_URL=${OLLAMA_BASE_URL}
   - Only set if explicitly defined in .env.docker

3. Application name: Mento → Memento (correct spelling)
   - Updated in: sidebar, README, deploy.sh, DOCKER_DEPLOYMENT.md

4. app/api/ai/config/route.ts - Return 'not set' instead of 'ollama'
   - Makes it clear when provider is not configured

IMPACT: The app will now properly use OpenAI when configured in the
admin interface, instead of silently falling back to Ollama.

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

keep-notes/DOCKER_DEPLOYMENT.md

@@ -1,6 +1,6 @@
 # 🐳 Docker Deployment Guide for Proxmox
 
-Complete guide to deploy Mento on Proxmox using Docker Compose.
+Complete guide to deploy Memento on Proxmox using Docker Compose.
 
 ## 📋 Prerequisites
 
@@ -375,7 +375,7 @@ usermod -aG docker ubuntu
 # Add: features: nesting=1,keyctl=1
 ```
 
-Then deploy Mento as described above.
+Then deploy Memento as described above.
 
 ## 📚 Additional Resources