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>

src/coinhunter/audit.py

@@ -0,0 +1,39 @@
+"""Audit logging for CoinHunter V2."""
+
+from __future__ import annotations
+
+import json
+from datetime import datetime, timezone
+from pathlib import Path
+from typing import Any
+
+from .config import load_config, resolve_log_dir
+from .runtime import RuntimePaths, ensure_runtime_dirs, get_runtime_paths, json_default
+
+_audit_dir_cache: dict[str, Path] = {}
+
+
+def _resolve_audit_dir(paths: RuntimePaths) -> Path:
+    key = str(paths.root)
+    if key not in _audit_dir_cache:
+        config = load_config(paths)
+        _audit_dir_cache[key] = resolve_log_dir(config, paths)
+    return _audit_dir_cache[key]
+
+
+def _audit_path(paths: RuntimePaths | None = None) -> Path:
+    paths = ensure_runtime_dirs(paths or get_runtime_paths())
+    logs_dir = _resolve_audit_dir(paths)
+    logs_dir.mkdir(parents=True, exist_ok=True)
+    return logs_dir / f"audit_{datetime.now(timezone.utc).strftime('%Y%m%d')}.jsonl"
+
+
+def audit_event(event: str, payload: dict[str, Any], paths: RuntimePaths | None = None) -> dict[str, Any]:
+    entry = {
+        "timestamp": datetime.now(timezone.utc).isoformat(),
+        "event": event,
+        **payload,
+    }
+    with _audit_path(paths).open("a", encoding="utf-8") as handle:
+        handle.write(json.dumps(entry, ensure_ascii=False, default=json_default) + "\n")
+    return entry