Add Ollama support for local LLM models (Phase 2 complete)

Major Changes:
- Added Ollama as alternative LLM provider to OpenAI
- Implemented flexible provider switching via environment variables
- Support for multiple embedding models (OpenAI and Ollama)
- Created comprehensive Ollama setup guide

Configuration Changes (config.py):
- Added LLM_PROVIDER and EMBEDDER_PROVIDER settings
- Added Ollama configuration: base URL, LLM model, embedding model
- Modified get_mem0_config() to dynamically switch providers
- OpenAI API key now optional when using Ollama
- Added validation to ensure required keys based on provider

Supported Configurations:
1. Full OpenAI (default):
   - LLM_PROVIDER=openai
   - EMBEDDER_PROVIDER=openai

2. Full Ollama (local):
   - LLM_PROVIDER=ollama
   - EMBEDDER_PROVIDER=ollama

3. Hybrid configurations:
   - Ollama LLM + OpenAI embeddings
   - OpenAI LLM + Ollama embeddings

Ollama Models Supported:
- LLM: llama3.1:8b, llama3.1:70b, mistral:7b, codellama:7b, phi3:3.8b
- Embeddings: nomic-embed-text, mxbai-embed-large, all-minilm

Documentation:
- Created docs/setup/ollama.mdx - Complete Ollama setup guide
  - Installation methods (host and Docker)
  - Model selection and comparison
  - Docker Compose configuration
  - Performance tuning and GPU acceleration
  - Migration guide from OpenAI
  - Troubleshooting section
- Updated README.md with Ollama features
- Updated .env.example with provider selection
- Marked Phase 2 as complete in roadmap

Environment Variables:
- LLM_PROVIDER: Select LLM provider (openai/ollama)
- EMBEDDER_PROVIDER: Select embedding provider (openai/ollama)
- OLLAMA_BASE_URL: Ollama API endpoint (default: http://localhost:11434)
- OLLAMA_LLM_MODEL: Ollama model for text generation
- OLLAMA_EMBEDDING_MODEL: Ollama model for embeddings
- MEM0_EMBEDDING_DIMS: Must match embedding model dimensions

Breaking Changes:
- None - defaults to OpenAI for backward compatibility

Migration Notes:
- When switching from OpenAI to Ollama embeddings, existing embeddings
  must be cleared due to dimension changes (1536 → 768 for nomic-embed-text)
- Update MEM0_EMBEDDING_DIMS to match chosen embedding model

Benefits:
✅ Cost savings - no API costs with local models
✅ Privacy - all data stays local
✅ Offline capability - works without internet
✅ Model variety - access to many open-source models
✅ Flexibility - easy switching between providers

Version: 1.1.0
Status: Phase 2 Complete - Production Ready with Ollama Support

🤖 Generated with Claude Code

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

.env.example

@@ -1,19 +1,31 @@
-# OpenAI Configuration
-OPENAI_API_KEY=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
+# LLM Provider Selection
+# Options: "openai" or "ollama"
+LLM_PROVIDER=openai
+EMBEDDER_PROVIDER=openai
 
+# OpenAI Configuration
+# Required when LLM_PROVIDER=openai or EMBEDDER_PROVIDER=openai
+OPENAI_API_KEY=sk-your-openai-api-key-here
+
+# Ollama Configuration
+# Required when LLM_PROVIDER=ollama or EMBEDDER_PROVIDER=ollama
+# Ollama must be running and models must be pulled
+OLLAMA_BASE_URL=http://localhost:11434
+OLLAMA_LLM_MODEL=llama3.1:8b
+OLLAMA_EMBEDDING_MODEL=nomic-embed-text
 
 # Supabase Configuration
-SUPABASE_CONNECTION_STRING=postgresql://postgres:CzkaYmRvc26Y@172.21.0.8:5432/postgres
+SUPABASE_CONNECTION_STRING=postgresql://user:password@host:5432/database
 
 # Neo4j Configuration
 NEO4J_URI=neo4j://neo4j:7687
 NEO4J_USER=neo4j
-NEO4J_PASSWORD=rH7v8bDmtqXP
+NEO4J_PASSWORD=your-neo4j-password
 
 # API Configuration
 API_HOST=0.0.0.0
 API_PORT=8080
-API_KEY=mem0_01KfV2ydPmwCIDftQOfx8eXgQikkhaFHpvIJrliW
+API_KEY=your-secure-api-key-here
 
 # MCP Server Configuration
 MCP_HOST=0.0.0.0