feat: perp bench cards on /perp/[slug] and /alternatives/[slug]

[Flotapponnier]

Summary

• Adds 4 bench cards (perp-fees, perp-funding, perp-active-markets, perp-fees-at-size) to all /perp/[slug] venue pages
• Renders the same bench cards on /alternatives/[slug] for perp venue slugs (gains, hyperliquid, etc.)
• Fixes perp-cost-slope ratio queries by adding ignoring(notional) to avoid label mismatch

Test plan

• /perp/gains shows 4 bench cards under "OpenChainBench rankings"
• /perp/hyperliquid shows bench cards with ranks
• /alternatives/gains shows "gains.trade across benchmarks" section with bench cards
• /alternatives/hyperliquid shows bench cards section
• Non-perp alternatives (e.g. /alternatives/ethereum) render without the bench cards section
• Build is clean (next build)

🤖 Generated with Claude Code

[Flotapponnier]

Wrong branch; reopening from the correct branch.