feat: add Claude backend with automatic Ollama fallback (Claudification Phase 1)

All agents now prefer Claude API when ANTHROPIC_API_KEY is configured,
with automatic fallback to Ollama when offline or unconfigured. New
src/anthropic/ module provides model selection via get_model() factory.

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

.env.example

@@ -8,7 +8,14 @@ API_HOST=0.0.0.0
 API_PORT=8000
 API_PREFIX=/v1
 
-# Ollama Configuration
+# Anthropic Configuration (Claude - preferred backend)
+# Set ANTHROPIC_API_KEY to enable Claude as the default backend
+# Without an API key, Tatlock uses Ollama exclusively
+# ANTHROPIC_API_KEY=sk-ant-api03-your-key-here
+ANTHROPIC_MODEL=claude-sonnet-4-20250514
+PREFER_CLOUD_BACKEND=true
+
+# Ollama Configuration (local fallback when Claude unavailable)
 OLLAMA_HOST=http://localhost:11434
 OLLAMA_DEFAULT_MODEL=mistral-nemo:latest
 OLLAMA_TIMEOUT=120
@@ -21,7 +28,6 @@ SEARXNG_TIMEOUT=30
 REDIS_HOST=localhost
 REDIS_PORT=6379
 REDIS_MEMORY_DB=1
-REDIS_BENCHMARK_DB=6
 REDIS_TIMEOUT=5
 
 # Qdrant Configuration
@@ -33,7 +39,6 @@ QDRANT_PORT=6333
 #   - development: DEBUG (maximum verbosity)
 #   - production: WARNING (minimal noise)
 # Uncomment to override: LOG_LEVEL=INFO
-ENABLE_BENCHMARKS=true
 # Note: Log format is auto-selected based on ENVIRONMENT (console for dev, json for production)
 
 # User Configuration