feat: Prevent duplicate climbs based on selected holds

[marcodejongh]

Summary

• Adds duplicate detection when saving climbs based on holds hash
• A duplicate is defined as a climb with the same holds AND same hold states, scoped to the same board type and layout
• Uses a holds_hash column with index for O(1) duplicate lookup instead of expensive JOINs

Changes

Database

• Added holds_hash column to board_climbs table
• Added composite index on (board_type, layout_id, holds_hash) for efficient lookups

Backend

• Created generateHoldsHash() utility that produces deterministic hashes from frames
• Updated saveClimb to check for duplicates before inserting
• Returns isDuplicate, existingClimbUuid, and existingClimbName if duplicate found
• Updated shared-sync to compute hash for new climbs and backfill existing ones

Frontend

• Added duplicate warning alert in create climb form
• Shows "View Existing Climb" button to navigate to the duplicate
• Provides "Dismiss" option to close the warning

Scripts

• Added backfill-holds-hash.ts script to populate hash for existing climbs

Test plan

• Create a new climb with unique holds → should save successfully
• Try to create a climb with identical holds → should show duplicate warning
• Click "View Existing Climb" → should navigate to the existing climb
• Create climb with same holds but different states (e.g., start vs hand) → should NOT be detected as duplicate
• Run npm run build:web → passes
• Apply migration with npm run db:migrate

🤖 Generated with Claude Code

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Project	Deployment	Review	Updated (UTC)
boardsesh	Building	Preview, Comment	Jan 24, 2026 0:09am

[claude]

Claude Review

✅ Ready to merge - Minor issues noted below, but nothing blocking.

Issues

1. Migration journal idx mismatch - packages/db/drizzle/meta/_journal.json:24: New migration uses idx: 37 but the previous entry is idx: 36. The journal already has non-sequential idx values (note idx 24-29 are out of order), so this is consistent with existing patterns, but worth awareness.

2. Unused import - packages/web/app/lib/api-wrappers/aurora/saveClimb.ts:5: convertLitUpHoldsStringToMap is imported and used, but climbHolds insert (lines 134-145) duplicates hold parsing logic that could fail silently for certain edge cases the conversion utility handles.

3. CSS class missing - packages/web/app/components/create-climb/moonboard-create-climb-form.tsx:304: References styles.holdCountsBar but the CSS module only defines styles.holdCounts - this will result in no styling being applied.

4. Backfill script updates one-by-one - packages/db/scripts/backfill-holds-hash.ts:93-103: Updates each climb individually in a loop. For large datasets, consider batching updates for performance.

5. Error message check fragile - packages/web/app/lib/api-wrappers/aurora/saveClimb.ts:102: Race condition handling checks for index name in error message string (board_climbs_holds_hash_unique_idx). This is fragile - different databases or pg versions may format errors differently. Consider catching specific PostgreSQL error code 23505 (unique_violation) instead.