feat: Add SOLID principles and TDD reference documentation

- Created solid.md to document the SOLID principles for clean code practices.
- Created tdd.md to outline Test Driven Development principles and practices.
- Added kana-rust-backend-best-practice.md as a reference guide for building a Rust backend using Axum and SeaORM.
- Established push-flow-convention.md to enforce pre-commit and pre-push hooks with versioning rules.
- Introduced AGENTS.md to provide guidance on best practices and available commands for Kilo.
- Configured kilo.json to include new skills and agents for enhanced functionality.
- Added lefthook.yml for managing git hooks to ensure code quality and adherence to conventions.

kilo.json

@@ -0,0 +1,16 @@
+{
+  "$schema": "https://app.kilo.ai/config.json",
+  "model": "anthropic/claude-sonnet-4-20250514",
+  "instructions": [
+    "AGENTS.md",
+    "CLAUDE.md"
+  ],
+  "skills": {
+    "paths": [
+      ".kilo/skills/clean-code",
+      ".kilo/skills/commit-convention",
+      ".kilo/skills/push-flow-convention",
+      ".kilo/skills/kana-rust-backend-best-practice"
+    ]
+  }
+}