feat: add self-update command and bump to 2.0.1

- Add `coinhunter update` CLI command for pipx/pip upgrade
- README: document update behavior and recommend pipx install
- Dynamic version badge with cacheSeconds=60
- Version bump: 2.0.0 → 2.0.1

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

src/coinhunter/cli.py

@@ -10,7 +10,7 @@ from . import __version__
 from .binance.spot_client import SpotBinanceClient
 from .binance.um_futures_client import UMFuturesClient
 from .config import ensure_init_files, get_binance_credentials, load_config
-from .runtime import get_runtime_paths, print_json
+from .runtime import get_runtime_paths, print_json, self_update
 from .services import account_service, market_service, opportunity_service, trade_service
 
 
@@ -102,6 +102,8 @@ def build_parser() -> argparse.ArgumentParser:
     scan_parser = opportunity_subparsers.add_parser("scan")
     scan_parser.add_argument("--symbols", nargs="*")
 
+    subparsers.add_parser("update", help="Upgrade coinhunter to the latest version")
+
     return parser
 
 
@@ -231,6 +233,10 @@ def main(argv: list[str] | None = None) -> int:
                 return 0
             parser.error("opportunity requires `portfolio` or `scan`")
 
+        if args.command == "update":
+            print_json(self_update())
+            return 0
+
         parser.error(f"Unsupported command {args.command}")
         return 2
     except Exception as exc: