fix: quality gate disabled at threshold 0; batch deletions; summary shows net count

- FRIGATE_SCORE_THRESHOLD=0.0 now fully disables the quality gate including the
  dynamic floor; a positive value is required to activate either
- Post-reconcile gate deletions are batched into one API call per person instead
  of one call per file
- Per-person summary reports gate removals and net uploaded count when the gate
  fires; grand summary includes total removed across all people
- .env.example comment updated to match the corrected opt-in behaviour

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.env.example

@@ -30,7 +30,7 @@ STRATEGY=auto
 # MIN_CONFIDENCE=0.7          # Minimum face detection confidence (default: 0.7)
 # BLUR_THRESHOLD=120.0        # Laplacian blur threshold; lower = accept more blur (default: 120.0)
 # MAX_AUTO_IMAGES=80          # Hard cap on auto-diversity selection (default: 80)
-# FRIGATE_SCORE_THRESHOLD=0.0 # Remove uploaded images scoring below this after upload (0 = disabled; skipped on cold start)
+# FRIGATE_SCORE_THRESHOLD=0.0 # Quality gate: remove images scoring below this after upload (0 = disabled; requires at least one prior run)
 
 # ── Caching & Models ──────────────────────────────────────────────────────────
 # FORCE_CPU=true              # Disable GPU, fall back to CPU