Rebuild bet sizing as a bottom sheet with situation-aware presets

Bet/Raise now opens a sheet whose presets follow the spot: open sizes
in BB (adjusted for limpers), 3bet/4bet multiples, postflop pot
fractions and raise multiples. Adds -/+ steppers with hold-to-repeat,
Min/All-in at the slider ends, and a square-curve slider so small sizes
stay precise with deep stacks. The hand view now exposes the street's
raise count so the client can tell a 3bet from a 4bet.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/hand.js

@@ -444,6 +444,7 @@ class Hand {
       pot: this.pot,
       potTotal: this.potTotal,
       currentBet: this.currentBet,
+      raises: this.raises, // ベット額の候補を 3bet・4bet などに合わせるため
       button: this.button,
       sbSeat: this.sbSeat,
       bbSeat: this.bbSeat,