Desktop board sizing, drop cascade, fast-stop/turbo fixes, bet button…

[WERSIT35]

…s, clean background

Reels / symbols (main.js, styles.css):

• Bigger symbols on desktop: board sized by height with a 3:2 (Pragmatic-style) shape and reference-like cell ratio; reclaim vertical space by compacting the control chrome; tighter frame padding + fill-the-cell symbol draw. Scoped to desktop (min-width:1000px) so the mobile stack is untouched.
• Vault-window transparent on desktop so the backdrop shows in the side margins.

Drop timing (main.js):

• Pronounced left-to-right reel cascade (~90ms/reel), turbo-scaled, collapses on fast-stop, applied to intro drop + tumble refills.
• Fix turbo "symbols vanish half-way" on both exit and entry: the drop awaits were double-scaling already-turbo-scaled durations, committing/hiding the board mid- fall. New _dropSettle waits the real (already-scaled) time.
• Fast-stop now smoothly accelerates the in-flight drop to a quick landing (_accelerateDrop preserves current progress) instead of teleporting to 0.75.

Bet +/- buttons (styles.css):

• Width-driven .bet-stepper (aspect-ratio 776/183, matching the real image) so the pill never letterboxes and the invisible round hit-zones land dead-on the drawn +/- circles at every size. Removed conflicting fixed heights.

Background (styles.css, ambiance.js):

• Clean, static, full-clarity temple backdrop: removed dark scrims, colour wash, vignette/scanline overlays, and the .altar backdrop-filter blur ("blended" look).
• Disabled the ambiance system entirely (animated nebulas/stars/floaters, deco gems, CSS mascot, pointer parallax).