Phase 1: Add upstream missing datatypes (URI, JSON, YDoc)

[AlexMikhalev]

Completed

• Add Uri, JSON, YDoc to DataType enum
• Add Uri, JSON, YDoc to Value enum
• Add datatype URLs to urls.rs
• Add check_valid_uri() function for URI validation
• Update serialization to handle new datatypes
• Add base64 encoding for YDoc values
• Resolve compilation errors

Next Steps

• Add normalize_value() and normalize_subresource() functions
• Add deprecation warnings to Value::Resource and SubResource::Resource
• Add feature flag for deprecated nested resources
• Add compatibility tests for old and new formats

Related: #3 (API Compatibility Strategy)