feat: configure full logging in webmain.py — all API logs to file + console

- RotatingFileHandler: logs/server_YYYY-MM-DD.log (50MB, keep 7 files)
- Console handler: colored timestamp + level + logger name + message
- webapp.* and rag_eval.* loggers captured at configured level
- uvicorn access/error logs also routed to same handlers
- File always captures DEBUG; console level controlled by --log-level arg
- Added --log-level and --log-file CLI arguments to webmain.py

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

webmain.py

@@ -5,13 +5,73 @@ and the same runs/ artifacts. Example:
 
     python webmain.py
     python webmain.py --host 0.0.0.0 --port 8800
+    python webmain.py --host 0.0.0.0 --port 8800 --log-level debug
 """
 
 from __future__ import annotations
 
 import argparse
+import logging
+import logging.config
+from datetime import datetime
+from pathlib import Path
 
-import uvicorn
+
+REPO_ROOT = Path(__file__).resolve().parent
+
+
+def _build_log_config(log_file: Path, level: str) -> dict:
+    """Build a uvicorn-compatible logging config dict.
+
+    Writes to both stderr (console) and a rotating daily log file.
+    All webapp.* and rag_eval.* loggers inherit from root so every
+    logger.info() call in the API routes is captured.
+    """
+    level_upper = level.upper()
+    return {
+        "version": 1,
+        "disable_existing_loggers": False,
+        "formatters": {
+            "detailed": {
+                "format": "%(asctime)s  %(levelname)-8s  %(name)s  %(message)s",
+                "datefmt": "%Y-%m-%d %H:%M:%S",
+            },
+            "console": {
+                "format": "%(asctime)s  %(levelname)-8s  %(name)-30s  %(message)s",
+                "datefmt": "%H:%M:%S",
+            },
+        },
+        "handlers": {
+            "console": {
+                "class": "logging.StreamHandler",
+                "stream": "ext://sys.stderr",
+                "formatter": "console",
+                "level": level_upper,
+            },
+            "file": {
+                "class": "logging.handlers.RotatingFileHandler",
+                "filename": str(log_file),
+                "maxBytes": 50 * 1024 * 1024,   # 50 MB per file
+                "backupCount": 7,                 # keep 7 rotated files
+                "encoding": "utf-8",
+                "formatter": "detailed",
+                "level": "DEBUG",                 # file always captures everything
+            },
+        },
+        "loggers": {
+            # Our application loggers — detailed level
+            "webapp": {"handlers": ["console", "file"], "level": level_upper, "propagate": False},
+            "rag_eval": {"handlers": ["console", "file"], "level": level_upper, "propagate": False},
+            # uvicorn access log — captured to file, shown on console
+            "uvicorn.access": {"handlers": ["console", "file"], "level": "INFO", "propagate": False},
+            "uvicorn.error": {"handlers": ["console", "file"], "level": "INFO", "propagate": False},
+            "uvicorn": {"handlers": ["console", "file"], "level": "INFO", "propagate": False},
+        },
+        "root": {
+            "handlers": ["console", "file"],
+            "level": "WARNING",   # suppress noisy third-party libs at WARNING
+        },
+    }
 
 
 def parse_args() -> argparse.Namespace:
@@ -24,17 +84,52 @@ def parse_args() -> argparse.Namespace:
         action="store_true",
         help="Enable auto-reload for local development.",
     )
+    parser.add_argument(
+        "--log-level",
+        default="info",
+        choices=["debug", "info", "warning", "error"],
+        help="Console log level (default: info). File always captures DEBUG.",
+    )
+    parser.add_argument(
+        "--log-file",
+        default=None,
+        help="Log file path (default: logs/server_YYYY-MM-DD.log).",
+    )
     return parser.parse_args()
 
 
 def main() -> None:
-    """Start uvicorn with the configured application."""
+    """Start uvicorn with the configured application and logging."""
+    import uvicorn
+
     args = parse_args()
+
+    # Resolve log file path
+    logs_dir = REPO_ROOT / "logs"
+    logs_dir.mkdir(parents=True, exist_ok=True)
+    if args.log_file:
+        log_file = Path(args.log_file)
+    else:
+        date_str = datetime.now().strftime("%Y-%m-%d")
+        log_file = logs_dir / f"server_{date_str}.log"
+
+    log_config = _build_log_config(log_file, args.log_level)
+
+    # Apply config before uvicorn starts so our loggers are ready immediately
+    logging.config.dictConfig(log_config)
+
+    logger = logging.getLogger("webapp.server")
+    logger.info(
+        "Starting RAGAS Console  host=%s  port=%d  log_level=%s  log_file=%s",
+        args.host, args.port, args.log_level, log_file,
+    )
+
     uvicorn.run(
         "webapp.server:app",
         host=args.host,
         port=args.port,
         reload=args.reload,
+        log_config=log_config,   # hand our config to uvicorn so it uses same handlers
     )