Add unique constraint on tapGestures(side, tapType) and use onConflictDoUpdate

[ng]

Summary

The setGesture procedure in settings.ts manually checks for existing gestures with a SELECT query before deciding to INSERT or UPDATE. This could be replaced with a database-level unique constraint and onConflictDoUpdate, which is both simpler and race-condition-safe.

Current Behavior (settings.ts:198-250)

// Check if gesture already exists
const existing = await db.select().from(tapGestures)
  .where(and(
    eq(tapGestures.side, input.side),
    eq(tapGestures.tapType, input.tapType)
  )).limit(1)

if (existing.length > 0) {
  // Update existing
} else {
  // Create new
}

Proposed Change

1. Migration: Add unique constraint on tapGestures(side, tapType)
2. Code: Replace the SELECT+branch with a single onConflictDoUpdate:

const [result] = await db
  .insert(tapGestures)
  .values(input)
  .onConflictDoUpdate({
    target: [tapGestures.side, tapGestures.tapType],
    set: { ...input, updatedAt: new Date() },
  })
  .returning()

Benefits

• Eliminates race condition (two concurrent requests could both see no existing record)
• Simpler code (one query instead of two)
• Database enforces the uniqueness invariant
• Consistent with the pattern used in device.ts for deviceState

Notes

• Requires a Drizzle migration to add the unique constraint
• Existing data should be checked for duplicates before migration
• Non-blocking improvement — current code works correctly under normal conditions

🤖 Generated with Claude Code