feat: system logs - email log + system log with admin UI

- db: email_logs (sent/failed) + system_logs (info/warn/error) tables,
  auto-migrated for existing installs
- backend/logger.js: logEmail/logSystem with try/catch (never breaks flow)
- mailer: log send result (SMTP unconfigured/sent/failed + error msg)
- webhook: log blocked-internal, non-2xx response, send failure
- server: error middleware records 500 errors to system_logs
- routes/logs.js: GET /logs/emails + /logs/system (admin/owner, filters)
- UI: 系统日志 page (owner/admin) with system/email tabs + filters
- API docs updated

backend/db.js

@@ -288,6 +288,30 @@ async function initSchema(connection) {
     INDEX idx_created (created_at)
   ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4`);
 
+  await createIfNotExists('email_logs', `CREATE TABLE email_logs (
+    id INT AUTO_INCREMENT PRIMARY KEY,
+    to_email VARCHAR(100) NOT NULL,
+    template_code VARCHAR(50) NOT NULL DEFAULT '',
+    subject VARCHAR(255) NOT NULL DEFAULT '',
+    status ENUM('sent','failed') NOT NULL,
+    error TEXT,
+    created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+    INDEX idx_email (to_email),
+    INDEX idx_created (created_at)
+  ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4`);
+
+  await createIfNotExists('system_logs', `CREATE TABLE system_logs (
+    id INT AUTO_INCREMENT PRIMARY KEY,
+    level ENUM('info','warn','error') NOT NULL DEFAULT 'info',
+    source VARCHAR(50) NOT NULL DEFAULT '',
+    message TEXT NOT NULL,
+    details TEXT,
+    created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+    INDEX idx_level (level),
+    INDEX idx_source (source),
+    INDEX idx_created (created_at)
+  ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4`);
+
   await seedTemplates(db);
   await migrateAdditions(db);
 }
@@ -318,6 +342,32 @@ async function migrateAdditions(db) {
       SELECT id, source, game_name, game_uid FROM users WHERE game_name != ''`);
   } catch {}
 
+  // 日志表(邮件日志 + 系统日志)
+  try {
+    await db.execute(`CREATE TABLE IF NOT EXISTS email_logs (
+      id INT AUTO_INCREMENT PRIMARY KEY,
+      to_email VARCHAR(100) NOT NULL,
+      template_code VARCHAR(50) NOT NULL DEFAULT '',
+      subject VARCHAR(255) NOT NULL DEFAULT '',
+      status ENUM('sent','failed') NOT NULL,
+      error TEXT,
+      created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+      INDEX idx_email (to_email),
+      INDEX idx_created (created_at)
+    ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4`);
+    await db.execute(`CREATE TABLE IF NOT EXISTS system_logs (
+      id INT AUTO_INCREMENT PRIMARY KEY,
+      level ENUM('info','warn','error') NOT NULL DEFAULT 'info',
+      source VARCHAR(50) NOT NULL DEFAULT '',
+      message TEXT NOT NULL,
+      details TEXT,
+      created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+      INDEX idx_level (level),
+      INDEX idx_source (source),
+      INDEX idx_created (created_at)
+    ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4`);
+  } catch {}
+
   try { await db.execute(`CREATE TABLE IF NOT EXISTS polls (id INT AUTO_INCREMENT PRIMARY KEY, title VARCHAR(200) NOT NULL, description TEXT, options JSON NOT NULL, group_name VARCHAR(100) NOT NULL DEFAULT '', server_name VARCHAR(100) NOT NULL DEFAULT '', start_time DATETIME, end_time DATETIME, active TINYINT(1) NOT NULL DEFAULT 1, created_by INT, created_at DATETIME DEFAULT CURRENT_TIMESTAMP, INDEX idx_active (active), INDEX idx_group_server (group_name, server_name)) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4`); } catch {}
   try { await db.execute(`CREATE TABLE IF NOT EXISTS poll_votes (id INT AUTO_INCREMENT PRIMARY KEY, poll_id INT NOT NULL, user_id INT NOT NULL, option_index INT NOT NULL, created_at DATETIME DEFAULT CURRENT_TIMESTAMP, UNIQUE KEY uk_poll_user (poll_id, user_id), INDEX idx_poll (poll_id)) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4`); } catch {}
   try { await db.execute(`CREATE TABLE IF NOT EXISTS feature_items (id INT AUTO_INCREMENT PRIMARY KEY, title VARCHAR(200) NOT NULL, description TEXT, group_name VARCHAR(100) NOT NULL DEFAULT '', server_name VARCHAR(100) NOT NULL DEFAULT '', status ENUM('pending','planned','done') NOT NULL DEFAULT 'pending', created_at DATETIME DEFAULT CURRENT_TIMESTAMP) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4`); } catch {}