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/bodybengirlpart2.json

@@ -2,31 +2,30 @@
   "action_id": "bodybengirlpart2",
   "action_name": "Bodybengirlpart2",
   "action": {
-    "full_body": "standing pose, bending forward at the waist while facing away from the camera",
-    "head": "turned backward looking over the shoulder",
-    "eyes": "looking directly at the viewer",
-    "arms": "extended downwards or resting on upper thighs",
-    "hands": "placed on knees or hanging freely",
-    "torso": "bent forward at a 90-degree angle, lower back arched",
-    "pelvis": "pushed back and tilted upwards",
-    "legs": "straight or slightly unlocked at the knees",
-    "feet": "standing firmly on the ground",
-    "additional": "view from behind, emphasizing hip curvature and flexibility"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "body suspended in mid-air, held by torso, bent over forward",
+    "head": "embarrassed, sweating, scared",
+    "eyes": "open, looking away or down",
+    "arms": "arms hanging down, limp arms, arms at sides",
+    "hands": "hands open, limp",
+    "torso": "torso grab, bent forward",
+    "pelvis": "hips raised if bent over",
+    "legs": "legs dangling, knees together, feet apart",
+    "feet": "feet off ground, dangling",
+    "additional": "motion lines, sweat drops"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/BodyBenGirlPart2.safetensors",
-    "lora_weight": 1.0,
-    "lora_triggers": "BodyBenGirlPart2"
+    "lora_weight": 0.9,
+    "lora_triggers": "bentstand-behind, dangling legs, dangling arms, from_side, arms hanging down, torso_grab, suspended"
   },
   "tags": [
-    "bent over",
-    "looking back",
-    "from behind",
-    "standing",
-    "flexible"
+    "torso_grab",
+    "suspension",
+    "bent_over",
+    "knees_together_feet_apart",
+    "arms_at_sides",
+    "motion_lines",
+    "embarrassed",
+    "sweat"
   ]
 }