fix: harden push subscription diagnostics

fix: support safari push subscription keys

fix: harden web push subscription flow

fix: pagination for history/PRs, rest day heatmap colors, calendar rest day markers, activity grid alignment

feat: quick-create exercise from workout picker

feat: exercise tab rework — modal for create/edit, body part badges, cleaner items

feat: exercise swap — replace exercise mid-workout via Repeat2 button

fix: plate calculator only shown for barbell/trap bar/EZ bar exercises

fix: accept comma as decimal separator in bodyweight input

feat: swipe left/right tab navigation with slide animation

feat: VAPID web push for lock-screen rest timer notifications

fix: async playDing, non-blocking finish(), short timer dev override

feat: show notification permission status in rest timer UI

fix: rest timer ding and SW notification fallback

feat: service worker — offline cache, rest-timer notifications, auto-reload on deploy