feat: Implement metadata system and reorganize project structure

✨ Features:
- Add comprehensive metadata system with YAML/JSON support
- Implement hierarchical metadata inheritance from parent folders
- Support plot-specific metadata overrides
- Add metadata caching for performance optimization

🗂️ Code Organization:
- Move Python orchestration code to orchestration/ folder
- Move validation utilities to tests/ folder
- Move documentation to docs/ folder
- Separate metadata functionality into dedicated module

🔧 Infrastructure:
- Add automatic asset copying to web directory
- Fix asset path resolution for nested directories
- Update template to use dynamic asset paths
- Add MetadataConfig class with inheritance options

📚 Documentation:
- Add comprehensive metadata usage guide (METADATA_USAGE.md)
- Add implementation documentation (METADATA_IMPLEMENTATION.md)
- Include example metadata files in examples/
- Add metadata validation utility script

🐛 Bug Fixes:
- Fix breadcrumb navigation and JavaScript functionality
- Resolve asset path issues in nested directories
- Update template imports for modular CSS/JS structure

This commit introduces a flexible metadata system that allows users to add
rich metadata to plots and folders using YAML or JSON files, with full
hierarchical inheritance and plot-specific overrides. The project structure
is now better organized with clear separation of concerns.

examples/specific_plot.json

@@ -0,0 +1,22 @@
+{
+  "title": "Specific Plot Analysis",
+  "description": "This metadata overrides folder metadata for this specific plot",
+  "plot_type": "histogram",
+  "variables": {
+    "x_axis": "invariant_mass",
+    "y_axis": "events",
+    "units": "GeV"
+  },
+  "selection": "signal_region",
+  "statistics": {
+    "entries": 125000,
+    "mean": 125.3,
+    "std_dev": 2.1
+  },
+  "tags": ["signal", "mass_peak", "important"],
+  "display": {
+    "highlight": true,
+    "featured": true,
+    "order_priority": 0
+  }
+}