fix: 全站 ruff 清零 — 77 errors → 0

Fixes:
- F821: install.py site_url 未定义(NameError)、sync_v2.py os 未导入、script_jobs.py LOG f-string
- F401: 移除 22 个未使用导入（models/__init__.py、install.py、auth.py 等）
- B904: 20 个 except 块 raise 添加 from e/from None
- S110: 20 个有意的 try-except-pass 添加 noqa 注释（SSH清理/DDL幂等/WS断连）
- B007: 3 个未使用循环变量重命名（dirs→_dirs、server_id→_server_id）
- F541: 3 个无占位符 f-string 修正
- F841: auth.py 未使用 ip_address 变量移除
- S105: auth_service.py Redis key prefix 误报 noqa
- B023: script_execution_flush.py 循环变量绑定修复

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

server/api/install.py

@@ -17,7 +17,7 @@ from urllib.parse import quote_plus
 from fastapi import APIRouter, HTTPException
 from pydantic import BaseModel
 from sqlalchemy import text
-from sqlalchemy.ext.asyncio import create_async_engine, async_sessionmaker, AsyncSession
+from sqlalchemy.ext.asyncio import create_async_engine
 
 from server.infrastructure.database.engine_compat import patch_aiomysql_do_ping
 
@@ -206,7 +206,7 @@ def _configure_guardian(install_dir: str, api_port: str) -> list[str]:
         log_dir.mkdir(parents=True, exist_ok=True)
         results.append(f"✓ 日志目录已创建 {log_dir}")
     except OSError:
-        results.append(f"✗ 日志目录创建失败（需 root 权限）")
+        results.append("✗ 日志目录创建失败（需 root 权限）")
 
     # 2. Supervisor config
     if bt_panel:
@@ -320,7 +320,6 @@ async def env_check():
     """Detect environment readiness — Python, MySQL client, Redis, write permissions."""
     _reject_post_install_wizard()
     import sys
-    import importlib
 
     checks = []
 
@@ -406,12 +405,13 @@ async def init_db(req: InitDbRequest):
 
     db_url = _make_db_url(req)
     redis_url = _build_redis_url(req)
+    site_url = req.site_url.rstrip("/") if req.site_url else f"http://127.0.0.1:{req.api_port}"
 
     try:
         patch_aiomysql_do_ping()
         engine = create_async_engine(db_url, pool_pre_ping=True, pool_recycle=300)
     except Exception as e:
-        raise HTTPException(400, f"数据库引擎创建失败: {e}")
+        raise HTTPException(400, f"数据库引擎创建失败: {e}") from e
 
     try:
         async with engine.begin() as conn:
@@ -435,7 +435,7 @@ async def init_db(req: InitDbRequest):
             for idx_sql in indexes:
                 try:
                     await conn.execute(text(idx_sql))
-                except Exception:
+                except Exception:  # noqa: S110 — DDL idempotent, may already exist
                     pass  # Index may already exist
 
             # Schema migrations for existing databases (safe — no-op if column exists)
@@ -445,7 +445,7 @@ async def init_db(req: InitDbRequest):
             for mig_sql in migrations:
                 try:
                     await conn.execute(text(mig_sql))
-                except Exception:
+                except Exception:  # noqa: S110 — DDL idempotent, may already exist
                     pass  # Column may already exist
 
             # Calculate pool_size from max_connections
@@ -462,7 +462,7 @@ async def init_db(req: InitDbRequest):
             secret_key = secrets.token_hex(32)
             api_key = secrets.token_hex(16)
             # Generate Fernet-compatible encryption key (32 url-safe base64 bytes)
-            import base64, hashlib
+            import base64
             encryption_key = base64.urlsafe_b64encode(secrets.token_bytes(32)).decode()
 
             # Insert settings
@@ -491,12 +491,11 @@ async def init_db(req: InitDbRequest):
 
     except Exception as e:
         await engine.dispose()
-        raise HTTPException(400, f"数据库初始化失败: {e}")
+        raise HTTPException(400, f"数据库初始化失败: {e}") from e
 
     await engine.dispose()
 
     # Write .env
-    site_url = req.site_url.rstrip("/") if req.site_url else f"http://127.0.0.1:{req.api_port}"
     _write_env(req, secret_key, api_key, encryption_key, pool_size, max_overflow, redis_url, site_url)
 
     # Write config.json
@@ -588,7 +587,7 @@ async def create_admin(req: CreateAdminRequest):
 
         await engine.dispose()
     except Exception as e:
-        raise HTTPException(400, f"创建管理员失败: {e}")
+        raise HTTPException(400, f"创建管理员失败: {e}") from e
 
     # Update config.json with brand
     if CONFIG_JSON.exists():
@@ -597,7 +596,7 @@ async def create_admin(req: CreateAdminRequest):
             config = json.loads(CONFIG_JSON.read_text())
             config["app_name"] = req.system_name
             CONFIG_JSON.write_text(json.dumps(config, indent=2, ensure_ascii=False))
-        except Exception:
+        except Exception:  # noqa: S110 — best-effort cleanup
             pass
 
     # Update .env with brand