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/hugkissingbreast_press_pov_illustrious_000005.json

@@ -2,34 +2,36 @@
   "action_id": "hugkissingbreast_press_pov_illustrious_000005",
   "action_name": "Hugkissingbreast Press Pov Illustrious 000005",
   "action": {
-    "full_body": "pov, close-up, leaning towards viewer, intimate interaction",
-    "head": "face close to camera, tilted head, kissing motion",
-    "eyes": "closed eyes, half-closed eyes, affectionate gaze",
-    "arms": "reaching forward, wrapping around viewer, arms visible on sides",
-    "hands": "hands on viewer's shoulders, hands behind viewer's neck, or out of frame",
-    "torso": "chest pressed against viewer, breasts squished, breast press",
-    "pelvis": "close proximity to viewer, angled forward",
-    "legs": "not visible or cropped",
+    "full_body": "POV close-up of a character hugging and kissing the viewer with breasts pressed against the 'camera'",
+    "head": "tilted forward, kissing expression, often with tongue or saliva trail, intense focus",
+    "eyes": "closed_eyes or looking_at_viewer, passionate gaze",
+    "arms": "arms_around_neck or reaching_towards_viewer, embracing the viewer",
+    "hands": "touching viewer's face or gripping shoulders (off-screen reference)",
+    "torso": "breast_press against the viewer, reduced distance",
+    "pelvis": "not visible (close-up)",
+    "legs": "not visible",
     "feet": "not visible",
-    "additional": "blush, saliva trail, deeply romantic atmosphere, soft lighting"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "additional": "intimate atmosphere, blushing, french_kiss, saliva_trail"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/Hugkissingbreast_press_pov_Illustrious-000005.safetensors",
-    "lora_weight": 1.0,
-    "lora_triggers": "Hugkissingbreast_press_pov_Illustrious-000005"
+    "lora_weight": 0.7,
+    "lora_triggers": "pov kiss, breast press"
   },
   "tags": [
     "pov",
+    "kiss",
+    "breast_press",
     "hug",
-    "kissing",
-    "breast press",
+    "french_kiss",
     "close-up",
-    "intimate",
-    "squeezing",
-    "couple"
+    "reaching_towards_viewer",
+    "arms_around_neck",
+    "closed_eyes",
+    "blush",
+    "saliva_trail",
+    "tongue",
+    "head_tilt",
+    "1girl"
   ]
 }