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/penis_under_mask_naixl_v1.json

@@ -2,35 +2,37 @@
   "action_id": "penis_under_mask_naixl_v1",
   "action_name": "Penis Under Mask Naixl V1",
   "action": {
-    "full_body": "close-up, sexual activity, fellatio,  or 1boy 1girl",
-    "head": "wearing face mask, surgical mask, penis in mouth, penis under mask, mask bulging, cheeks bulging, saliva trail",
-    "eyes": "half-closed eyes, upturned eyes, teary eyes, or ahegao",
-    "arms": "arms resting or holding partner",
-    "hands": "hands guiding head or pulling down mask strap",
-    "torso": "upper body, collarbone, exposed chest",
-    "pelvis": "crotch shot, focus on insertion",
-    "legs": "kneeling or out of frame",
-    "feet": "out of frame",
-    "additional": "interior mouth view obscured, fabric stretching, distortion"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "kneeling, squatting, or sitting",
+    "head": "wearing surgical_mask or mouth_veil, penis positioned under the mask material",
+    "eyes": "open_eyes, looking_at_viewer, penis_awe",
+    "arms": "reaching towards face, or resting",
+    "hands": "mask_pull (pulling mask away from face), penis_grab",
+    "torso": "facing viewer or from_side, leaning forward",
+    "pelvis": "hips steady",
+    "legs": "kneeling or bent",
+    "feet": "resting",
+    "additional": "saliva, precume, tongue_out, licking_penis"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/Penis_under_Mask_NAIXL_v1.safetensors",
     "lora_weight": 1.0,
-    "lora_triggers": "Penis_under_Mask_NAIXL_v1"
+    "lora_triggers": "penis_under_mask"
   },
   "tags": [
-    "penis under mask",
-    "face mask",
-    "surgical mask",
-    "fellatio",
-    "oral sex",
-    "bulge in mask",
-    "mask pull",
-    "obscured face",
-    "nsfw"
+    "penis_under_mask",
+    "surgical_mask",
+    "penis_on_face",
+    "imminent_fellatio",
+    "mask_pull",
+    "licking_penis",
+    "penis_grab",
+    "open_mouth",
+    "tongue_out",
+    "saliva",
+    "mouth_veil",
+    "squatting",
+    "kneeling",
+    "pov",
+    "looking_at_viewer"
   ]
 }