Add core service infrastructure

- NATS event bus (pub/sub, JetStream, KV storage)
- Service registry with health monitoring
- Base service class with lifecycle management
- Config system
- Logger with Vi formatting

Adapted from Lyra's patterns, namespace changed to vi.*

🦊💕

core/logger.py

@@ -0,0 +1,73 @@
+import logging
+import sys
+import os
+from datetime import datetime
+from logging.handlers import TimedRotatingFileHandler
+
+
+class ViFormatter(logging.Formatter):
+    """Custom formatter for Vi services with symbolic level indicators"""
+    def format(self, record):
+        timestamp = datetime.now().strftime('%H:%M:%S')
+        level_map = {
+            'DEBUG': '·',
+            'INFO': '✓',
+            'WARNING': '⚠',
+            'ERROR': '✗',
+            'CRITICAL': '☠'
+        }
+        level_symbol = level_map.get(record.levelname, '?')
+        return f"[{timestamp}] {level_symbol} {record.getMessage()}"
+
+
+def _get_project_root():
+    """Find the project root directory by looking for core/ directory"""
+    current_dir = os.path.dirname(os.path.abspath(__file__))
+    return os.path.dirname(current_dir)
+
+
+def setup_logger(name="vi", level=logging.INFO, service_name=None):
+    """Set up a logger with console and optional file output"""
+    # Allow environment variable to override log level
+    env_level = os.getenv('LOG_LEVEL', '').upper()
+    if env_level in ['DEBUG', 'INFO', 'WARNING', 'ERROR']:
+        level = getattr(logging, env_level)
+    
+    logger = logging.getLogger(name)
+    
+    if logger.handlers:
+        return logger
+    
+    logger.setLevel(level)
+    
+    # Console handler
+    console_handler = logging.StreamHandler(sys.stdout)
+    console_handler.setFormatter(ViFormatter())
+    logger.addHandler(console_handler)
+    
+    # File handler with daily rotation if service_name is specified
+    if service_name:
+        project_root = _get_project_root()
+        logs_dir = os.path.join(project_root, 'logs')
+        
+        if not os.path.exists(logs_dir):
+            os.makedirs(logs_dir, exist_ok=True)
+        
+        log_file = os.path.join(logs_dir, f"{service_name}.log")
+        
+        file_handler = TimedRotatingFileHandler(
+            log_file,
+            when='midnight',
+            interval=1,
+            backupCount=30,
+            encoding='utf-8'
+        )
+        file_handler.setFormatter(ViFormatter())
+        logger.addHandler(file_handler)
+    
+    logger.propagate = False
+    
+    return logger
+
+
+logger = setup_logger()