async/await, catch{} without binding, and ?? are all syntax errors in
Safari 9 (iOS 9). A single syntax error prevents the entire script from
parsing, so connect() never ran — explaining 'nicht verbunden'.

Removed / replaced every incompatible construct:
- async/await  → .then()/.catch() Promise chains
- catch {}     → catch(_e) {} (optional catch binding is ES2019)
- ??           → explicit != null ternary (nullish coalescing is ES2020)
- padStart()   → pad2() helper (String.prototype.padStart is ES2017,
                 not available in iOS < 10)
- scrollIntoView({block,behavior}) → scrollIntoView(true) (options
  object not supported in iOS 9, boolean form works everywhere)

Template literals, arrow functions, const/let, forEach, classList,
dataset, Promise, WebSocket, Canvas, performance.now() and
requestAnimationFrame are all fine in iOS 9.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>