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/res_facial.json

@@ -2,32 +2,32 @@
   "action_id": "res_facial",
   "action_name": "Res Facial",
   "action": {
-    "full_body": "upper body portrait shot, character is leaning slightly forward toward the camera",
-    "head": "facing directly at the viewer, chin slightly tucked",
-    "eyes": "intense gaze, looking directly into the camera",
-    "arms": "bent upwards at the elbows",
-    "hands": "palms resting gently against cheeks or framing the face to emphasize the expression",
-    "torso": "upper torso visible, facing forward",
-    "pelvis": "not visible",
-    "legs": "not visible",
-    "feet": "not visible",
-    "additional": "soft lighting highlighting facial contours"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "1girl, 2boys, restrained, forced",
+    "head": "head_grab, hand_on_another's_face, head_back",
+    "eyes": "eyes_closed",
+    "arms": "arms_behind_back",
+    "hands": "bound_wrists",
+    "torso": "upper_body",
+    "pelvis": "standing",
+    "legs": "standing",
+    "feet": "standing",
+    "additional": "facial, bukkake, cum, cum_on_hair, penis"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/res_facial.safetensors",
-    "lora_weight": 1.0,
-    "lora_triggers": "res_facial"
+    "lora_weight": 0.8,
+    "lora_triggers": "restrained_facial"
   },
   "tags": [
-    "close-up",
-    "portrait",
-    "looking_at_viewer",
-    "face_focus",
-    "touching_face",
-    "detailed_eyes"
+    "restrained",
+    "forced",
+    "head_grab",
+    "hand_on_another's_face",
+    "grabbing_from_behind",
+    "facial",
+    "bukkake",
+    "cum_on_hair",
+    "eyes_closed",
+    "2boys"
   ]
 }