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/gyaru_bitch_illustrious.json

@@ -2,32 +2,31 @@
   "action_id": "gyaru_bitch_illustrious",
   "action_name": "Gyaru Bitch Illustrious",
   "action": {
-    "full_body": "standing pose, upper body leaning slightly forward to accentuate curves, confident and flashy posture",
-    "head": "tilted slightly to the side, chin down",
-    "eyes": "looking directly at viewer, heavy makeup, possibly winking",
-    "arms": "raised, elbows bent outwards",
-    "hands": "double peace sign, v-sign near face, aggressive finger splay",
-    "torso": "arched back significantly, emphasized chest",
-    "pelvis": "hips cocked to one side",
-    "legs": "standing with weight on one leg, other leg slightly bent at knee",
-    "feet": "planted firmly",
-    "additional": "exuding a haughty or teasing 'gal' atmosphere, flashy accessories"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "F"
+    "full_body": "standing, energetic pose, looking_at_viewer",
+    "head": "blonde_hair, heavy_makeup, smiling, tanned_skin",
+    "eyes": "eyelashes, eyeshadow",
+    "arms": "hand_on_hip, arm_up",
+    "hands": "v_sign, long_fingernails",
+    "torso": "animal_print, revealing_clothes, cleavage, navel",
+    "pelvis": "short_skirt, hips",
+    "legs": "tanned_legs, standing",
+    "feet": "high_heels",
+    "additional": "jewelry, necklace, earrings"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/Gyaru_bitch_illustrious.safetensors",
     "lora_weight": 1.0,
-    "lora_triggers": "Gyaru_bitch_illustrious"
+    "lora_triggers": "gyaru bitch, gyaru"
   },
   "tags": [
-    "double peace sign",
     "gyaru",
-    "smug",
-    "tongue out",
-    "leaning forward",
-    "tan"
+    "dark_skin",
+    "animal_print",
+    "long_fingernails",
+    "makeup",
+    "blonde_hair",
+    "jewelry",
+    "revealing_clothes",
+    "navel"
   ]
 }