1.9.1

release: v1.9.1 - signal server domain, scroll fidelity, h-scroll

- shared/constants.ts + web-viewer: switch signal server default from
  http://152.67.122.105:3456 to https://titan.xtapo.org so the public
  endpoint is HTTPS (PWA viewer requires it for getUserMedia / service
  workers) and no longer leaks the origin VM's IP.

- input-handler.ts: stop quantizing wheel deltas to ±3. Browsers report
  deltaMode 0 (pixels), 1 (lines), or 2 (pages) — earlier we tossed the
  magnitude with Math.sign, so a fast wheel flick scrolled exactly as
  much as a slow nudge. Translate to "lines" with deltaMode-aware math
  (~33 px per line on Windows pixel-mode mice, raw lines on Firefox/
  Linux, pages × 10 for keyboard PageDown emulation), preserving a
  1-tick floor in the direction of motion so trackpad nudges still
  register.

- input-executor.ts: forward deltaX through nutMouse.scrollLeft/Right
  so horizontal scroll works on hosts (matters for code editors with
  long lines, kanban boards, wide spreadsheets — previously dropped).