feat(logging): add configurable logging with file output support

Introduce --log-level and --log-file CLI arguments.
Add execution time tracking and detailed logs across all modules.

src/uipath_explainator/config.py

@@ -2,6 +2,7 @@ from __future__ import annotations
 
 from dataclasses import dataclass
 from pathlib import Path
+import logging
 import re
 from typing import Self
 
@@ -9,6 +10,9 @@ from dotenv import load_dotenv
 import os
 
 
+logger = logging.getLogger(__name__)
+
+
 @dataclass(slots=True)
 class Settings:
     api_key: str | None
@@ -18,19 +22,29 @@ class Settings:
     @classmethod
     def from_env(cls, env_file: Path | None = None, model_override: str | None = None) -> Self:
         if env_file:
+            logger.info("Loading environment variables from %s", env_file)
             load_dotenv(env_file)
         else:
+            logger.debug("Loading environment variables using default dotenv lookup")
             load_dotenv()
 
-        return cls(
+        settings = cls(
             api_key=os.getenv("GEMINI_API_KEY") or os.getenv("GOOGLE_API_KEY"),
             base_url=os.getenv("GEMINI_BASE_URL") or None,
             model=model_override or os.getenv("GEMINI_MODEL") or "gemini-2.5-flash",
         )
+        logger.info(
+            "Configuration loaded: model=%s base_url=%s api_key=%s",
+            settings.model,
+            settings.normalized_base_url() or "<default>",
+            "set" if settings.api_key else "missing",
+        )
+        return settings
 
     def require_api_key(self) -> None:
         if not self.api_key:
             raise ValueError("Missing GEMINI_API_KEY (or GOOGLE_API_KEY) in the environment.")
+        logger.debug("Gemini API key is available")
 
     def normalized_base_url(self) -> str | None:
         if not self.base_url: