refactor: rewrite to CoinHunter V2 flat architecture

Replace the V1 commands/services split with a flat, direct architecture:
- cli.py dispatches directly to service functions
- New services: account, market, trade, opportunity
- Thin Binance wrappers: spot_client, um_futures_client
- Add audit logging, runtime paths, and TOML config
- Remove legacy V1 code: commands/, precheck, review engine, smart executor
- Add ruff + mypy toolchain and fix edge cases in trade params

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.gitignore

@@ -1,8 +1,35 @@
+# Python
 __pycache__/
-*.pyc
+*.py[cod]
+*$py.class
 .pytest_cache/
+.mypy_cache/
+.ruff_cache/
+.coverage
+htmlcov/
+
+# Virtual environments
 .venv/
+venv/
+
+# Build artifacts
 dist/
 build/
 *.egg-info/
+
+# IDE / editors
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+
+# OS files
+.DS_Store
+
+# Secrets / local env
+.env
+*.env
+
+# Claude local overrides
 .claude/skills/gstack/