Features:
- Manual entry form above data list
- Date picker with auto-load existing entries
- Upsert logic: creates new or updates existing entry
- Smart button text: "Hinzufügen" vs "Aktualisieren"
- Prevents duplicate entries per day
- Feature enforcement for nutrition_entries
Backend:
- POST /nutrition - Create or update entry (upsert)
- GET /nutrition/by-date/{date} - Load entry by date
- Auto-detects existing entry and switches to UPDATE mode
- Increments usage counter only on INSERT
Frontend:
- EntryForm component with date picker + macros inputs
- Auto-loads data when date changes
- Shows info message when entry exists
- Success/error feedback
- Disabled state while loading/saving
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>