Improve trainer recovery and terrain gearing

[ridecontrol]

What changed

• makes trainer, heart-rate, and controller pairing attempts cancellable and makes forgetting a device update the UI immediately
• coalesces live FTMS resistance commands, waits for matching control acknowledgements, and cleanly reconnects after transport failures
• gives required FTMS setup a trainer-appropriate timeout while retaining fast runtime command failure recovery
• prevents advertisements received during an active handshake from collapsing retry backoff into a reconnect loop
• removes route-specific base resistance and applies one shared grade-driven terrain target before virtual gearing
• recalibrates the 24 physical gear ratios, keeps modest climbs easy in gear 1, and improves resistance chart scaling

Why

Recent rides exposed stalled Bluetooth states, stale command queues, aggressive service-discovery timeouts, and resistance that remained too high in low gears. Route-specific resistance baselines also conflicted with the shared terrain and virtual-gearing model.

Impact

Trainer connections recover more predictably across FTMS-compatible hardware, pairing can always be stopped or forgotten, and terrain load is derived consistently from grade with the selected virtual gear applied afterward.

Validation

• bun run ci
• Biome clean with warnings treated as errors
• Tailwind diagnostics passed
• 270 unit tests passed
• TypeScript check passed
• production build passed