chore: консолидация незакоммиченной работы (биохимия + System Health + lab/textbooks)

Зафиксирована накопленная незакоммиченная работа рабочего дерева, КРОМЕ файлов
учебника «Химия 7» (migration 046, chemistry_7_*.html, chem7_svg.js, тест —
оставлены незакоммиченными по запросу).

Включает: модуль биохимии (ядро BIO, 3D VSEPR, химдвижок, баланс, challenges,
пути из БД), System Health Level 1 (вердикт/мониторинг), а также frontend-
страницы и lab/textbooks-правки параллельной сессии.

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

backend/src/controllers/adminController.js

@@ -610,47 +610,105 @@ function clearErrorLog(req, res) {
 const os = require('os');
 const path = require('path');
 const fs = require('fs');
-const { DB_PATH, UPLOADS_DIR } = require('../config');
+const { execSync } = require('child_process');
+const { monitorEventLoopDelay } = require('perf_hooks');
+const sse = require('../sse');
+const { DB_PATH, UPLOADS_DIR, NODE_ENV } = require('../config');
+
+// Монитор лага event-loop (включается один раз при загрузке модуля).
+const _eluMonitor = monitorEventLoopDelay({ resolution: 20 });
+_eluMonitor.enable();
+
+// Версия приложения + git-commit (кэшируются один раз).
+const _appVersion = (() => { try { return require('../../package.json').version; } catch { return '?'; } })();
+const _gitCommit = (() => {
+  try { return execSync('git rev-parse --short HEAD', { cwd: __dirname, stdio: ['ignore', 'pipe', 'ignore'] }).toString().trim(); }
+  catch { return null; }
+})();
+
+function _dirSize(dir) {
+  let total = 0;
+  try { for (const f of fs.readdirSync(dir)) { try { total += fs.statSync(path.join(dir, f)).size; } catch {} } } catch {}
+  return total;
+}
+
+// Топ таблиц БД по числу строк (исключая служебные sqlite_* и _migrations).
+function _dbTables() {
+  try {
+    const tables = db.prepare(
+      "SELECT name FROM sqlite_master WHERE type='table' AND name NOT LIKE 'sqlite_%' AND name NOT LIKE '\\_%' ESCAPE '\\'"
+    ).all();
+    const rows = tables.map(t => {
+      let n = 0;
+      try { n = db.prepare(`SELECT COUNT(*) AS n FROM "${t.name}"`).get().n; } catch {}
+      return { name: t.name, rows: n };
+    });
+    rows.sort((a, b) => b.rows - a.rows);
+    return rows.slice(0, 12);
+  } catch { return []; }
+}
 
 function getHealth(_req, res) {
   const uptimeSec = process.uptime();
-  let dbSizeBytes = 0;
-  try { dbSizeBytes = fs.statSync(DB_PATH).size; } catch {}
-  let uploadsSizeBytes = 0;
-  try {
-    const files = fs.readdirSync(UPLOADS_DIR);
-    for (const f of files) {
-      try { uploadsSizeBytes += fs.statSync(path.join(UPLOADS_DIR, f)).size; } catch {}
-    }
-  } catch {}
+  const mem = process.memoryUsage();
+  const dbSizeBytes  = (() => { try { return fs.statSync(DB_PATH).size; } catch { return 0; } })();
+  const walSizeBytes = (() => { try { return fs.statSync(DB_PATH + '-wal').size; } catch { return 0; } })();
+  const uploadsSizeBytes = _dirSize(UPLOADS_DIR);
 
-  const totalUsers   = db.prepare('SELECT COUNT(*) AS n FROM users').get().n;
-  const todaySessions = db.prepare("SELECT COUNT(*) AS n FROM test_sessions WHERE started_at >= date('now')").get().n;
-  const totalSessions = db.prepare('SELECT COUNT(*) AS n FROM test_sessions').get().n;
+  // Свободное место на разделе, где лежит БД.
+  let disk = null;
+  try { const s = fs.statfsSync(path.dirname(path.resolve(DB_PATH))); disk = { freeBytes: s.bavail * s.bsize, totalBytes: s.blocks * s.bsize }; } catch {}
+
+  const totalMem = os.totalmem(), freeMem = os.freemem();
+  const memPercent = totalMem ? (totalMem - freeMem) / totalMem : 0;
+  const eventLoopLagMs = _eluMonitor.mean / 1e6;
+
+  const totalUsers     = db.prepare('SELECT COUNT(*) AS n FROM users').get().n;
+  const todaySessions  = db.prepare("SELECT COUNT(*) AS n FROM test_sessions WHERE started_at >= date('now')").get().n;
+  const totalSessions  = db.prepare('SELECT COUNT(*) AS n FROM test_sessions').get().n;
   const totalQuestions = db.prepare('SELECT COUNT(*) AS n FROM questions').get().n;
-  const recentErrors  = db.prepare("SELECT COUNT(*) AS n FROM error_log WHERE created_at >= datetime('now', '-24 hours')").get().n;
+  const recentErrors   = db.prepare("SELECT COUNT(*) AS n FROM error_log WHERE created_at >= datetime('now', '-24 hours')").get().n;
+
+  let sseStats = { users: 0, guests: 0, connections: 0 };
+  try { sseStats = sse.stats(); } catch {}
+
+  // Вердикт здоровья по порогам.
+  const reasons = [];
+  let status = 'ok';
+  const warn = (m) => { reasons.push(m); if (status === 'ok') status = 'warning'; };
+  const crit = (m) => { reasons.push(m); status = 'critical'; };
+  if (memPercent > 0.92)      crit(`Память ${Math.round(memPercent * 100)}%`);
+  else if (memPercent > 0.80) warn(`Память ${Math.round(memPercent * 100)}%`);
+  if (disk) {
+    if (disk.freeBytes < 500e6)    crit('Мало места на диске (<500 МБ)');
+    else if (disk.freeBytes < 2e9) warn('Места на диске <2 ГБ');
+  }
+  if (recentErrors > 50)     crit(`${recentErrors} ошибок за 24ч`);
+  else if (recentErrors > 5) warn(`${recentErrors} ошибок за 24ч`);
+  if (eventLoopLagMs > 200)      crit(`Лаг event-loop ${eventLoopLagMs.toFixed(0)} мс`);
+  else if (eventLoopLagMs > 70)  warn(`Лаг event-loop ${eventLoopLagMs.toFixed(0)} мс`);
+  if (dbSizeBytes > 1.5e9) warn('БД >1.5 ГБ');
 
   res.json({
+    status, reasons,
     uptime: uptimeSec,
-    memory: {
-      rss: process.memoryUsage().rss,
-      heapUsed: process.memoryUsage().heapUsed,
-    },
-    db: {
-      sizeBytes: dbSizeBytes,
-      totalUsers,
-      totalSessions,
-      todaySessions,
-      totalQuestions,
-    },
-    uploads: {
-      sizeBytes: uploadsSizeBytes,
-    },
+    startedAt: new Date(Date.now() - uptimeSec * 1000).toISOString(),
+    memory: { rss: mem.rss, heapUsed: mem.heapUsed, heapTotal: mem.heapTotal },
+    memPercent, eventLoopLagMs,
+    loadavg: os.loadavg(),
+    disk,
+    db: { sizeBytes: dbSizeBytes, walBytes: walSizeBytes, totalUsers, totalSessions, todaySessions, totalQuestions, tables: _dbTables() },
+    uploads: { sizeBytes: uploadsSizeBytes },
+    sse: sseStats,
     node: process.version,
     platform: os.platform(),
+    arch: os.arch(),
     cpus: os.cpus().length,
-    freeMem: os.freemem(),
-    totalMem: os.totalmem(),
+    freeMem, totalMem,
+    pid: process.pid,
+    env: NODE_ENV,
+    version: _appVersion,
+    commit: _gitCommit,
     recentErrors,
   });
 }