test: add comprehensive authentication middleware test (issue #4)

- Add Test 5 to integration_test.sh for authentication verification
- Test admin endpoints reject unauthorized requests properly
- Test admin endpoints work with valid JWT tokens
- Test KV endpoints respect anonymous access configuration
- Extract and use auto-generated root account tokens

docs: update README and CLAUDE.md for recent security features

- Document allow_anonymous_read and allow_anonymous_write config options
- Update API documentation with authentication requirements
- Add security notes about DELETE operations always requiring auth
- Update configuration table with new anonymous access settings
- Document new authentication test coverage in CLAUDE.md

🤖 Generated with [Claude Code](https://claude.ai/code)

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

CLAUDE.md

@@ -99,15 +99,21 @@ type StoredValue struct {
 
 ### Configuration Architecture
 
-The system uses feature toggles extensively (`types/Config:271-276`):
+The system uses feature toggles extensively (`types/Config:271-280`):
 ```yaml
 auth_enabled: true              # JWT authentication system
 tamper_logging_enabled: true    # Cryptographic audit trail  
 clustering_enabled: true        # Gossip protocol and sync
 rate_limiting_enabled: true     # Per-client rate limiting
 revision_history_enabled: true  # Automatic versioning
+
+# Anonymous access control (Issue #5 - when auth_enabled: true)
+allow_anonymous_read: false     # Allow unauthenticated read access to KV endpoints
+allow_anonymous_write: false    # Allow unauthenticated write access to KV endpoints
 ```
 
+**Security Note**: DELETE operations always require authentication when `auth_enabled: true`, regardless of anonymous access settings.
+
 ### Testing Strategy
 
 #### Integration Test Suite (`integration_test.sh`)
@@ -115,6 +121,11 @@ revision_history_enabled: true  # Automatic versioning
 - **Basic functionality** - Single-node CRUD operations  
 - **Cluster formation** - 2-node gossip protocol and data replication
 - **Conflict resolution** - Automated conflict detection and resolution using `test_conflict.go`
+- **Authentication middleware** - Comprehensive security testing (Issue #4):
+  - Admin endpoints properly reject unauthenticated requests
+  - Admin endpoints work with valid JWT tokens
+  - KV endpoints respect anonymous access configuration
+  - Automatic root account creation and token extraction
 
 The test suite uses sophisticated retry logic and timing to handle the eventually consistent nature of the system.