feat(ccip): automation + reference quality — keep identity flowing hands-free (#114)

Works through the optional CCIP ideas + the "keep moving even if I forget" ask:

AUTOMATION (no button needed):
- Hourly beat auto-enqueues CCIP backfill — new images get embedded (and errored
  ones retried) on their own; the queue never goes idle waiting for a click.
- CCIP auto-apply: a daily sweep tags confident matches (source='ccip_auto') so
  identity tags keep flowing. ON by default (opt-out, like head auto-apply);
  ml_settings.ccip_auto_apply_enabled + _threshold (0.92, above the suggest cut),
  migration 0064. Vectorized (one matmul + reduceat per image), reversible, skips
  already-applied/rejected. Switch + threshold in the GPU agent card; GET/PATCH
  /api/ml/settings; auto_applied count in /api/ccip/overview.

REFERENCE QUALITY (the over-fire root cause):
- character_references now draws ONLY from single-character images — on a
  multi-character image the tag is image-level, so every figure would otherwise
  pollute each character's prototypes (a 2-char image tagged 'Velma' made
  Daphne's figure a Velma reference). This is the contamination behind residual
  over-firing.
- Cached on a cheap signature (char-tag count + ccip-region count/max-id) so the
  reference load isn't redone on every modal open.

Tests: multi-character image not used as a reference; auto-apply tags a confident
match as ccip_auto.

NEXT (not done, confirmed): comic-panel cropping + SigLIP concept crops ("spot
interesting content").

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ttrj5P7upUTueSfoJcxEqa

backend/app/api/ml_admin.py

@@ -22,6 +22,8 @@ _EDITABLE = (
     "head_auto_apply_enabled",
     "head_auto_apply_min_positives",
     "ccip_match_threshold",
+    "ccip_auto_apply_enabled",
+    "ccip_auto_apply_threshold",
 )
 
 
@@ -50,6 +52,8 @@ async def get_settings():
             "head_auto_apply_enabled": s.head_auto_apply_enabled,
             "head_auto_apply_min_positives": s.head_auto_apply_min_positives,
             "ccip_match_threshold": s.ccip_match_threshold,
+            "ccip_auto_apply_enabled": s.ccip_auto_apply_enabled,
+            "ccip_auto_apply_threshold": s.ccip_auto_apply_threshold,
         }
     )
 
@@ -119,6 +123,8 @@ def _validate(p: dict) -> str | None:
         return "head_auto_apply_min_positives must be >= 1"
     if not (0.5 <= float(p["ccip_match_threshold"]) <= 0.999):
         return "ccip_match_threshold must be between 0.5 and 0.999"
+    if not (0.5 <= float(p["ccip_auto_apply_threshold"]) <= 0.999):
+        return "ccip_auto_apply_threshold must be between 0.5 and 0.999"
     return None