Refactor gallery generator with smart file handling and improved UI

Key improvements:
- Add intelligent file update checking with 30-second buffer to avoid unnecessary operations
- Implement efficient PDF to PNG conversion (only when source is newer)
- Add smart file copying (skip if target is up-to-date)
- Create proper folder structure using plot_root/source_name pattern
- Improve template with better text handling for long plot names
- Add text wrapping, truncation, and hover tooltips for plot names
- Remove unnecessary directory cleaning for true incremental updates
- Fix title display issue (was showing '.' instead of 'Gallery')
- Add comprehensive logging showing what's processed vs skipped

Performance benefits:
- Subsequent runs are significantly faster (only processes changed files)
- Reduces ImageMagick conversions and file I/O operations
- Maintains file system timing robustness with buffer delays

UI improvements:
- Better handling of long filenames with word wrapping
- Constrained text areas prevent overlap between thumbnails
- Hover tooltips show full names when truncated
- Responsive grid layout maintained

config.py

@@ -0,0 +1,64 @@
+from dataclasses import dataclass, field, asdict
+from pathlib import Path
+
+import yaml
+
+
+@dataclass
+class GalleryItem:
+    name: str
+    path: Path
+
+
+@dataclass
+class Config:
+    web_folder: str = ""
+    backup_folder: str = ""
+    png_dpi: int = 400
+    plot_root: str = "gallery"
+    sources: list[GalleryItem] = field(default_factory=list)
+
+    @classmethod
+    def from_yaml(cls, yaml_file: str) -> "Config":
+        """
+        Load configuration from a YAML file.
+
+        Args:
+            yaml_file (str): Path to the YAML file.
+            strict (bool):
+                If True, raises an error if a key in the YAML file does not exist in the Config class.
+                If False (default), adds all keys as attributes
+
+        Returns:
+            Config: Instance of this class
+        """
+
+        with open(yaml_file, "r") as f:
+            new_config: dict = yaml.safe_load(f)
+
+        new_config["sources"] = [
+            GalleryItem(name=src["name"], path=Path(src["path"]))
+            for src in new_config.get("sources", False)
+        ]
+
+        instance = cls(**{
+            k: v
+            for k, v in new_config.items()
+        })
+
+        return instance
+
+    def to_yaml(self, yaml_file: str) -> None:
+        """
+        Save the current configuration to a YAML file.
+
+        Args:
+            yaml_file (str): Path to the YAML file.
+        """
+        with open(yaml_file, "w") as f:
+            yaml.dump(asdict(self), f, default_flow_style=False)
+
+
+if __name__ == "__main__":
+    config = Config()
+    config.to_yaml("config.yaml")