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/closeup_facial_illus.json

@@ -2,32 +2,30 @@
   "action_id": "closeup_facial_illus",
   "action_name": "Closeup Facial Illus",
   "action": {
-    "full_body": "extreme close-up portrait shot framing the face and upper neck, macro focus",
-    "head": "facing directly forward, highly detailed facial micro-expressions, blush",
-    "eyes": "intense gaze, intricate iris details, looking at viewer, eyelashes focus",
-    "arms": "not visible",
-    "hands": "not visible",
-    "torso": "upper collarbone area only",
-    "pelvis": "not visible",
-    "legs": "not visible",
-    "feet": "not visible",
-    "additional": "illustrative style, shallow depth of field, soft lighting, detailed skin texture, vibrant colors"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "close-up, portrait",
+    "head": "facial, open_mouth, tongue, saliva, blush",
+    "eyes": "looking_at_viewer, eyes_open",
+    "arms": "out_of_frame",
+    "hands": "out_of_frame",
+    "torso": "out_of_frame",
+    "pelvis": "out_of_frame",
+    "legs": "out_of_frame",
+    "feet": "out_of_frame",
+    "additional": "nsfw, semen, cum"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/Closeup_Facial_iLLus.safetensors",
     "lora_weight": 1.0,
-    "lora_triggers": "Closeup_Facial_iLLus"
+    "lora_triggers": "Closeup Facial"
   },
   "tags": [
+    "facial",
     "close-up",
     "portrait",
-    "face focus",
-    "illustration",
-    "detailed eyes",
-    "macro"
+    "open_mouth",
+    "tongue",
+    "looking_at_viewer",
+    "saliva",
+    "blush"
   ]
 }