feat: non-blocking bulk-add, CORS hardening, credential preset access control (#31)

* devices: hide discovered neighbors that are already managed

Discovered Devices showed every unresolved MikroTik neighbor, even when
the neighbor was obviously the same device a managed node is reporting
through a different link / MAC / alias. Since we already know every
managed device interface MAC, primary IP, and system identity, we can
flag those rows.

- /api/devices/discovered now annotates each row with duplicate_of_device_id
  and duplicate_of_device_name when the neighbor matches a managed device
  by interface MAC, primary IP, or system identity.
- Add a Hide duplicates of managed devices toggle (default on) above the
  table, with a count of how many matches were found. When enabled, the
  list hides matched rows; when disabled, matches stay visible but are
  dimmed and tagged Already managed so the origin is clear.
- Suppress the Add to Manager action for rows that are already a
  managed device, since adding them would create a second record for the
  same hardware.

Co-authored-by: Denis <denis-ev@users.noreply.github.com>

* devices: safer duplicate handling, try-all safeguards, and timezone/firmware fixes

Co-authored-by: Denis <denis-ev@users.noreply.github.com>

* Non-blocking follow-ups: parsePort util, tests, bulk-add queue, preset rate limit

Co-authored-by: Denis <denis-ev@users.noreply.github.com>

* fix(security): tighten CORS, Redis rate limits, and preset access controls

Require explicit CORS origins in production, align Socket.IO CORS with HTTP,
default Docker Compose to local HTTPS origins, and remove the in-memory
mutation limiter in favor of Redis. Also add operator-use flags for credential
presets in the UI and harden bulk-add job access and client error messages.

Co-authored-by: Denis <denis-ev@users.noreply.github.com>

---------

Co-authored-by: Cursor Agent <cursoragent@cursor.com>

backend/src/utils/corsOrigins.ts

@@ -0,0 +1,103 @@
+import type { CorsOptions } from 'cors';
+
+/** Browser dev servers and typical local access through nginx. */
+const DEFAULT_DEV_ORIGINS = [
+  'http://localhost:3000',
+  'http://127.0.0.1:3000',
+  'http://localhost:5173',
+  'http://127.0.0.1:5173',
+  'http://localhost',
+  'http://127.0.0.1',
+  'https://localhost',
+  'https://127.0.0.1',
+];
+
+type Resolved =
+  | { kind: 'wildcard' }
+  | { kind: 'list'; allowed: string[] };
+
+function parseList(raw: string): string[] {
+  return raw.split(',').map((s) => s.trim()).filter(Boolean);
+}
+
+function resolveCors(): Resolved {
+  const nodeEnv = process.env.NODE_ENV || 'development';
+  const raw = process.env.CORS_ORIGIN?.trim();
+
+  if (raw === '*') {
+    if (nodeEnv === 'production') {
+      console.error(
+        'CORS_ORIGIN=* is not allowed in production. Set a comma-separated list of browser origins (e.g. https://manager.example.com).',
+      );
+      process.exit(1);
+    }
+    return { kind: 'wildcard' };
+  }
+
+  if (!raw) {
+    if (nodeEnv === 'production') {
+      console.error(
+        'CORS_ORIGIN is required in production (comma-separated origins, e.g. https://manager.example.com).',
+      );
+      process.exit(1);
+    }
+    if (nodeEnv === 'test') {
+      return { kind: 'wildcard' };
+    }
+    return { kind: 'list', allowed: DEFAULT_DEV_ORIGINS };
+  }
+
+  return { kind: 'list', allowed: parseList(raw) };
+}
+
+let resolvedCache: Resolved | null = null;
+
+function getResolved(): Resolved {
+  if (!resolvedCache) resolvedCache = resolveCors();
+  return resolvedCache;
+}
+
+/** Clears memoized CORS resolution (for Jest when env changes between cases). */
+export function resetCorsResolvedCacheForTests(): void {
+  resolvedCache = null;
+}
+
+/** Express `cors` middleware options (no `origin: *` with `credentials: true`). */
+export function corsMiddlewareOptions(): CorsOptions {
+  const resolved = getResolved();
+  if (resolved.kind === 'wildcard') {
+    return { origin: '*', credentials: false };
+  }
+  const allowed = resolved.allowed;
+  return {
+    origin(origin, callback) {
+      if (!origin) {
+        callback(null, true);
+        return;
+      }
+      if (allowed.includes(origin)) {
+        callback(null, true);
+        return;
+      }
+      callback(null, false);
+    },
+    credentials: true,
+  };
+}
+
+/** Socket.IO server `cors` field — must align with HTTP CORS. */
+export function socketIoCorsOptions(): {
+  origin: string | string[];
+  methods: string[];
+  credentials: boolean;
+} {
+  const resolved = getResolved();
+  if (resolved.kind === 'wildcard') {
+    return { origin: '*', methods: ['GET', 'POST'], credentials: false };
+  }
+  return {
+    origin: resolved.allowed,
+    methods: ['GET', 'POST'],
+    credentials: true,
+  };
+}