Fixes calculate_protein_g_per_kg and calculate_protein_days_in_target:
**Problem:**
Both functions were treating individual nutrition_log entries as days,
causing incorrect calculations when multiple entries exist per day
(e.g., from CSV imports: 233 entries across 7 days).
**Solution:**
1. calculate_protein_g_per_kg:
- Added GROUP BY date, SUM(protein_g) to aggregate by day
- Now averages daily totals, not individual entries
- Correct: 7 days → 7 values, not 233 entries → 233 values
2. calculate_protein_days_in_target:
- Added GROUP BY date, SUM(protein_g) to aggregate by day
- Calculates target range in absolute grams (not g/kg per entry)
- Counts unique DAYS in range, not entries
- Correct format: "5/7" (5 of 7 days), not "150/233" (entries)
**Impact:**
- protein_g_per_kg: was returning "nicht verfügbar" → now returns correct value
- protein_days_in_target: was returning "nicht verfügbar" → now returns correct format
**Root Cause:**
Functions expected 7 unique dates but got 233 entries.
With export date 2026-04-02 and last data 2026-03-26,
the 7-day window had insufficient unique dates.
Issue reported by user: Part B placeholders not showing correct values
in extended export (registry metadata was correct, but computed values failed).
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>