feat: 接入同花顺官方SDK，新增v2数据接口，股票详情K线改用v2(前复权日K)

- vendor 同花顺官方 SDK 到 backend/sdk（含K线>10年自动切片、重试、拼音首字母检索兜底）
- 新增 /api/v2 路由：行情/估值/财务/日历/指数/K线/标的检索
- 股票详情页K线改用 v2 同花顺接口（前复权日K+总手+按昨收涨跌幅）
- 密钥仅后端持有，响应/日志无泄露
- 新增 run_local.sh 本地直接拉起（不再依赖 docker）

backend/sdk/credentials.py

@@ -0,0 +1,101 @@
+from __future__ import annotations
+
+import os
+import sys
+from collections.abc import Mapping
+from pathlib import Path
+
+CANONICAL_API_KEY_ENV = "HITHINK_FINANCE_API_KEY"
+# AUV 项目自有约定：同花顺 key 存在 .env 的 fuyao_apikey（由 load_dotenv 加载）
+PROJECT_API_KEY_ENV = "fuyao_apikey"
+LEGACY_API_KEY_ENVS = ("FUYAO_TOKEN", "API_KEY")
+
+
+class CredentialFileError(RuntimeError):
+    """Raised when the user credential file exists but cannot be read safely."""
+
+
+def credential_file_path(
+    *,
+    platform: str | None = None,
+    env: Mapping[str, str] | None = None,
+    home: Path | None = None,
+) -> Path:
+    resolved_platform = platform or sys.platform
+    resolved_env = env if env is not None else os.environ
+    resolved_home = home or Path.home()
+
+    if resolved_platform == "win32":
+        config_root = resolved_env.get("APPDATA", "").strip()
+        base = Path(config_root) if config_root else resolved_home / "AppData" / "Roaming"
+    elif resolved_platform == "darwin":
+        base = resolved_home / "Library" / "Application Support"
+    else:
+        config_root = resolved_env.get("XDG_CONFIG_HOME", "").strip()
+        base = Path(config_root).expanduser() if config_root else resolved_home / ".config"
+    return base / "hithink-finance" / "credentials.env"
+
+
+def _non_blank(value: str | None) -> str | None:
+    if value is None:
+        return None
+    stripped = value.strip()
+    return stripped or None
+
+
+def _read_credential_file(path: Path) -> str | None:
+    if not path.exists():
+        return None
+    try:
+        content = path.read_text(encoding="utf-8")
+    except OSError as exc:
+        raise CredentialFileError(
+            f"Unable to read hithink finance credential file: {path}"
+        ) from exc
+
+    for line_number, raw_line in enumerate(content.splitlines(), start=1):
+        line = raw_line.strip()
+        if not line or line.startswith("#") or "=" not in line:
+            continue
+        name, value = line.split("=", 1)
+        if name.strip() != CANONICAL_API_KEY_ENV:
+            continue
+        normalized = value.strip()
+        if "'" in normalized or '"' in normalized:
+            raise CredentialFileError(
+                f"Invalid hithink finance credential file at {path}:{line_number}: "
+                f"{CANONICAL_API_KEY_ENV} must not be quoted."
+            )
+        return _non_blank(normalized)
+    return None
+
+
+def resolve_api_key(
+    *,
+    env: Mapping[str, str] | None = None,
+    credential_path: Path | None = None,
+) -> str | None:
+    resolved_env = env if env is not None else os.environ
+
+    canonical = _non_blank(resolved_env.get(CANONICAL_API_KEY_ENV))
+    if canonical is not None:
+        return canonical
+
+    # AUV 项目约定：优先读 .env 的 fuyao_apikey
+    project_key = _non_blank(resolved_env.get(PROJECT_API_KEY_ENV))
+    if project_key is not None:
+        return project_key
+
+    stored = _read_credential_file(
+        credential_path
+        if credential_path is not None
+        else credential_file_path(env=resolved_env)
+    )
+    if stored is not None:
+        return stored
+
+    for name in LEGACY_API_KEY_ENVS:
+        legacy = _non_blank(resolved_env.get(name))
+        if legacy is not None:
+            return legacy
+    return None