Prefer device-reported speed on the Analysis tab, with per-device unit settings

[Jbithell]

Summary

The Analysis tab's "Speed over time" chart and Average/Maximum speed cards were computed entirely by differentiating consecutive GPS position samples (distance / time between fixes). This amplifies ordinary GPS position jitter into large speed spikes — e.g. a boat holding a steady course under autopilot was showing a 21.6 mph "maximum speed" that never actually happened.

Devices already send their own reported speed (stored in Events.data.location.speed), but the Analysis loader never read it.

• Added two new per-device settings under Admin → Devices:
  • Input speed — the unit the device's own reported speed is sent in (knots / km/h / m/s / mph), or "Not reported" to keep the existing calculated-only behaviour.
  • Display speed — the unit speeds are shown in throughout the Analysis tab for that device.
• The Analysis loader now prefers the device's reported speed per point when an input unit is configured, falling back to the position-derived calculation only for points that lack a reported value (a reported value of exactly 0 is indistinguishable from "field absent," so those still fall back).
• A warning banner appears on the chart whenever some readings had to fall back to the calculated (potentially noisy) speed, explaining why.
• The existing GPS-jitter outlier filter still applies, but only to the calculated fallback values — device-reported speeds are trusted outright.
• The map route coloring, legend, and chart axis all respect the device's chosen display unit.

Test plan

• npx tsc -b — no new type errors (two pre-existing, unrelated errors remain in timingPoints.tsx/timingPointsHistoricComparison.tsx)
• Generated and applied the Drizzle migration locally (npm run db:generate / wrangler d1 migrations apply --local)
• Seeded a local device with inputSpeedUnit: kts, displaySpeedUnit: mph and synthetic events with steady 6 kt reported speed but GPS-jittered positions — Analysis tab showed a smooth ~7 mph line with spikes only at the points where reported speed was deliberately missing, each correctly flagged by the warning banner
• Seeded a second device with no input speed unit configured — Analysis tab shows the original derived-only behaviour and no warning banner (backward compatible default)
• Verified Admin → Devices create/edit forms persist both new settings correctly
• Verified switching a device's display unit (e.g. to knots) updates the chart, summary cards, legend, and map popup consistently

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Generated by Claude Code

[Copilot]

Pull request overview

This PR improves speed-related analytics on the Analysis tab by preferring device-reported speed readings (when configured per device) and standardizing speed unit conversion/display across charts, cards, and map coloring. This reduces GPS-jitter-induced spikes from position-derived speed while keeping backward compatibility for devices that don’t report speed.

Changes:

• Added per-device inputSpeedUnit (nullable) and displaySpeedUnit (default "mph") to persist speed unit preferences.
• Updated the Analysis loader/UI to use device-reported speed when available, fall back to derived speed when not, and show a warning banner when fallback was needed.
• Centralized speed unit conversion/labels and updated map route coloring + legend to respect the selected display unit.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
website/database/schema/Devices.ts	Adds inputSpeedUnit and displaySpeedUnit columns to the Devices schema.
website/database/migrations/0010_flashy_amphibian.sql	Migration to add the two new device speed unit columns.
website/database/migrations/meta/0010_snapshot.json	Drizzle snapshot update reflecting the schema change.
website/database/migrations/meta/_journal.json	Adds migration journal entry for 0010_flashy_amphibian.
website/app/utils/speedUnits.ts	Introduces shared speed unit constants, labels, and conversion helpers.
website/app/routes/date/analysis.tsx	Loads per-device speed settings, prefers device speed with derived fallback, updates chart/cards/alert behavior, and passes unit metadata to map.
website/app/routes/admin/devices.tsx	Adds Admin UI + server parsing/persistence for the new per-device speed unit settings.
website/app/components/AnalysisMap/speedColor.ts	Generalizes legend/range utilities away from mph-specific naming to support arbitrary display units.
website/app/components/AnalysisMap/AnalysisMap.tsx	Adds optional speedUnit prop passthrough to the client map.
website/app/components/AnalysisMap/AnalysisMap.client.tsx	Uses display-speed values for coloring and formats popup speed using the selected display unit.

Suppressed comments (1)

website/app/routes/date/analysis.tsx:414

• pointsWithDerivedSpeed is now populated with resolved speeds (device-reported when available, otherwise derived), so the name is misleading after this change. Renaming it (e.g. pointsWithResolvedSpeed) would make the code easier to follow and avoid confusion when reasoning about the device/derived fallback behavior.

  const pointsWithDerivedSpeed = pointRows.map((point) => ({
    id: Number(point.id),
    timestamp: Number(point.timestamp),
    latitude: Number(point.latitude),
    longitude: Number(point.longitude),
    speedMps: 0,
  }));

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