Initial stable release

• Initial stable release of YrestAPI: universal API for high-speed delivery of JSON object lists, defined by .yml model config files at the database query layer.
• Read-only JSON API endpoints: /api/index and /api/count.
• /api/index supports filters, sorting, pagination, and nested relation paths.
• /api/count supports the same filter semantics as /api/index.
• Declarative YAML model system with relations: has_one, has_many, belongs_to, polymorphic belongs_to, through.
• Preset-driven JSON shaping, including nested presets.
• Formatter and computable field support.
• Integration test dataset and smoke coverage for complex relations.
• Recursive relation guardrails with reentrant and max_depth.