Add Checkpoints Gallery with per-checkpoint generation settings

- New Checkpoint model (slug, name, checkpoint_path, data JSON, image_path)
- sync_checkpoints() loads metadata from data/checkpoints/*.json and falls
  back to template defaults for models without a JSON file
- _apply_checkpoint_settings() applies per-checkpoint steps, CFG, sampler,
  base positive/negative prompts, and VAE (with dynamic VAELoader node
  injection for non-integrated VAEs) to the ComfyUI workflow
- Bulk Create from Checkpoints: scans Illustrious/Noob model directories,
  reads matching HTML files, uses LLM to populate metadata, falls back to
  template defaults when no HTML is present
- Gallery index with batch cover generation and WebSocket progress bar
- Detail page showing Generation Settings and Base Prompts cards
- Checkpoints nav link added to layout
- New data/prompts/checkpoint_system.txt LLM system prompt
- Updated README with all current galleries and file structure
- Also includes accumulated action/scene JSON updates, new actions, and
  other template/generator improvements from prior sessions

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

data/actions/small_dom_big_sub.json

@@ -2,36 +2,30 @@
   "action_id": "small_dom_big_sub",
   "action_name": "Small Dom Big Sub",
   "action": {
-    "full_body": "two characters, extreme size difference, height difference, small character standing confidently, large character kneeling submissively, giantess trope aesthetic",
-    "head": "tilted down, looking down, tilted up, looking up, eye contact",
-    "eyes": "condescending gaze, adoring gaze, locking eyes",
-    "arms": "arms crossed, hands on hips, arms resting on thighs",
-    "hands": "hands on hips, hands on knees",
-    "torso": "straight posture, leaning forward, hulking frame vs petite frame",
-    "pelvis": "facing forward, angled slightly",
-    "legs": "standing straight, kneeling, bent knees",
-    "feet": "flat on ground, toes on ground",
-    "additional": "low angle, perspective exaggeration, comparison"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "Small male clinging to the back of a standing large female in a piggyback position",
+    "head": "Male head resting near female's neck or shoulder",
+    "eyes": "Closed or looking at partner",
+    "arms": "Male arms wrapped tightly around female's neck or shoulders",
+    "hands": "Clasped or holding on to shoulders",
+    "torso": "Male torso pressed against female's back",
+    "pelvis": "Engaged in sex from behind",
+    "legs": "Male legs locked around female's waist in a leg lock",
+    "feet": "Dangling or hooked behind female",
+    "additional": "Significant size difference creates a stark contrast between partners"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/Small_Dom_Big_Sub.safetensors",
-    "lora_weight": 1.0,
-    "lora_triggers": "Small_Dom_Big_Sub"
+    "lora_weight": 0.8,
+    "lora_triggers": "SDBS_V1, piggyback, small male, huge female, size difference"
   },
   "tags": [
-    "size difference",
-    "height difference",
-    "kneeling",
-    "standing",
-    "looking up",
-    "looking down",
-    "female domination",
-    "duo",
-    "minigirl",
-    "giantess"
+    "piggyback",
+    "standing_sex",
+    "sex_from_behind",
+    "miniboy",
+    "giantess",
+    "size_difference",
+    "leg_lock",
+    "carrying"
   ]
 }