feat: implement production-ready features from improvement plan phase 2.5 & 2.6

Phase 2.5: Fix Foundation (CRITICAL)
- Fixed 4 failing tests by adding cache attribute to mock_client fixture
- Created comprehensive cache tests for Pages endpoint (test_pages_cache.py)
- Added missing dependencies: pydantic[email] and aiohttp to core requirements
- Updated requirements.txt with proper dependency versions
- Achieved 82.67% test coverage with 454 passing tests

Phase 2.6: Production Essentials
- Implemented structured logging (wikijs/logging.py)
  * JSON and text log formatters
  * Configurable log levels and output destinations
  * Integration with client operations

- Implemented metrics and telemetry (wikijs/metrics.py)
  * Request tracking with duration, status codes, errors
  * Latency percentiles (min, max, avg, p50, p95, p99)
  * Error rate calculation
  * Thread-safe metrics collection

- Implemented rate limiting (wikijs/ratelimit.py)
  * Token bucket algorithm for request throttling
  * Per-endpoint rate limiting support
  * Configurable timeout handling
  * Burst capacity management

- Created SECURITY.md policy
  * Vulnerability reporting procedures
  * Security best practices
  * Response timelines
  * Supported versions

Documentation
- Added comprehensive logging guide (docs/logging.md)
- Added metrics and telemetry guide (docs/metrics.md)
- Added rate limiting guide (docs/rate_limiting.md)
- Updated README.md with production features section
- Updated IMPROVEMENT_PLAN_2.md with completed checkboxes

Testing
- Created test suite for logging (tests/test_logging.py)
- Created test suite for metrics (tests/test_metrics.py)
- Created test suite for rate limiting (tests/test_ratelimit.py)
- All 454 tests passing
- Test coverage: 82.67%

Breaking Changes: None
Dependencies Added: pydantic[email], email-validator, dnspython

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

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

docs/logging.md

@@ -0,0 +1,89 @@
+# Logging Guide
+
+## Overview
+
+The wikijs-python-sdk includes structured logging capabilities for production monitoring and debugging.
+
+## Configuration
+
+### Basic Setup
+
+```python
+from wikijs import WikiJSClient
+import logging
+
+# Enable debug logging
+client = WikiJSClient(
+    "https://wiki.example.com",
+    auth="your-api-key",
+    log_level=logging.DEBUG
+)
+```
+
+### JSON Logging
+
+```python
+from wikijs.logging import setup_logging
+
+# Setup JSON logging to file
+logger = setup_logging(
+    level=logging.INFO,
+    format_type="json",
+    output_file="wikijs.log"
+)
+```
+
+### Text Logging
+
+```python
+from wikijs.logging import setup_logging
+
+# Setup text logging to console
+logger = setup_logging(
+    level=logging.INFO,
+    format_type="text"
+)
+```
+
+## Log Levels
+
+- `DEBUG`: Detailed information for debugging
+- `INFO`: General informational messages
+- `WARNING`: Warning messages
+- `ERROR`: Error messages
+- `CRITICAL`: Critical failures
+
+## Log Fields
+
+JSON logs include:
+- `timestamp`: ISO 8601 timestamp
+- `level`: Log level
+- `message`: Log message
+- `module`: Python module
+- `function`: Function name
+- `line`: Line number
+- `extra`: Additional context
+
+## Example Output
+
+```json
+{
+  "timestamp": "2025-10-23T10:15:30.123456",
+  "level": "INFO",
+  "logger": "wikijs",
+  "message": "Initializing WikiJSClient",
+  "module": "client",
+  "function": "__init__",
+  "line": 45,
+  "base_url": "https://wiki.example.com",
+  "timeout": 30
+}
+```
+
+## Best Practices
+
+1. Use appropriate log levels
+2. Enable DEBUG only for development
+3. Rotate log files in production
+4. Monitor error rates
+5. Include contextual information