[mixn1998]

Summary:

• Add an inline edit action only for today's weight history row
• Reuse the existing same-day revision ledger so earlier values remain auditable
• Recalculate the latest value, chart, and moving average from the corrected effective record
• Keep historical dates read-only and remove temporary design documentation

Validation:

• npm run typecheck
• npm test (159 passed)
• npm run build
• Browser QA for edit, invalid-value protection, and cancel