Fix fee tiers to match official Hyperliquid docs
Perps tiers 4-6 had wrong volume thresholds, taker rates, and
incorrect negative maker rebates (HL only has rebates via staking).
Changes (matching https://hyperliquid.gitbook.io/.../trading/fees):
Tier 4: $250M→$500M vol, taker 0.025%→0.028%
Tier 5: $750M→$2B vol, taker 0.020%→0.026%, maker -0.002%→0.000%
Tier 6: $2.5B→$7B vol, taker 0.015%→0.024%, maker -0.004%→0.000%
UI dropdown labels updated to match. Chart refresh enhanced with
resize+fitContent after recalc for smooth transitions.
ramseshk
055da97a79