Render rates directionally across dashboard surfaces

[LandynDev]

Stored rates are canonical "spoke per 1 SOL" in BOTH direction quotes; the UI was rendering reverse-leg values as if per-direction — off by ~476x (e.g. BTC->SOL showing 0.0021 instead of ~476) and sorting reverse legs worst-first.

• Shared boundary helpers: format.ts directionalRate/rateUnit/isReverseLeg (canonical_pair rule, lockstep with python), MinersDashboard directionalRateFor/rateUnitFor
• Converted at ingest so EMA/Tukey/y-ranges share the directional scale: marketRate completedPoints, MarketRateChart crown line + tooltips, CrownRateChart panels, CrownDirectionSegment (ticker + sticky header), CrownGridHoverCard
• Fixed value + unit + sort/best-deal on MinerRatesTable, OrderbookDepth, RateQuoteHelper (incl. the copyable jq snippet: reverse sorts ascending and zero/null quotes filtered), MinerDetailHeader, RateHistoryTable
• One rateUnit source for every TO/FROM suffix

Verified: tsc + vite build, prettier.