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

backup.py

@@ -0,0 +1,23 @@
+import zipfile
+import datetime
+from pathlib import Path
+
+WEB_FOLDER = Path("plots")
+BACKUP_FOLDER = Path("backups")
+
+today = datetime.date.today().strftime("%Y%m%d")
+backup_name = f"backup-{today}.zip"
+backup_path = BACKUP_FOLDER / backup_name
+
+BACKUP_FOLDER.mkdir(parents=True, exist_ok=True)
+
+if backup_path.exists():
+    print(f"Backup already exists: {backup_path}")
+else:
+    print(f"Creating backup: {backup_path}")
+    with zipfile.ZipFile(backup_path, "w", zipfile.ZIP_DEFLATED) as zipf:
+        for path in WEB_FOLDER.rglob("*"):
+            if path.is_file():
+                arcname = path.relative_to(WEB_FOLDER.parent)
+                zipf.write(path, arcname)
+    print("✅ Backup complete.")