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/nm_fullmouthcum_ill.json

@@ -2,34 +2,36 @@
   "action_id": "nm_fullmouthcum_ill",
   "action_name": "Nm Fullmouthcum Ill",
   "action": {
-    "full_body": "portrait or upper body shot focusing on facial distortion",
-    "head": "face flushed, cheeks bulging significantly, puffy cheeks, stuffed cheeks, lips pursed or slightly leaking liquid",
-    "eyes": "tearing up, watery eyes, squashed or wide open depending on intensity",
-    "arms": "optional, hands often near face",
-    "hands": "wiping mouth or framing face, messy with liquid",
-    "torso": "visible upper chest",
-    "pelvis": "not visible or kneeling",
-    "legs": "not visible",
-    "feet": "not visible",
-    "additional": "mouth full, holding breath, white liquid dripping, semen in mouth, cum drip, excess saliva, struggling to swallow"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "focus on face",
+    "head": "tilted back, open_mouth, visible uvula",
+    "eyes": "half-closed_eyes, rolled_up_eyes",
+    "arms": "",
+    "hands": "",
+    "torso": "",
+    "pelvis": "",
+    "legs": "",
+    "feet": "",
+    "additional": "cum_in_mouth, cum_on_tongue, excessive_cum, saliva, facial, full_mouth"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/NM_FullMouthCum_ill.safetensors",
     "lora_weight": 1.0,
-    "lora_triggers": "NM_FullMouthCum_ill"
+    "lora_triggers": "nm_fullmouthcum"
   },
   "tags": [
-    "stuffed cheeks",
-    "puffy cheeks",
-    "mouth full",
-    "cum in mouth",
-    "bulging cheeks",
-    "semen in mouth",
-    "holding breath",
-    "cheeks"
+    "cum_in_mouth",
+    "cum_on_tongue",
+    "full_mouth",
+    "excessive_cum",
+    "facial",
+    "bukkake",
+    "after_fellatio",
+    "open_mouth",
+    "tongue_out",
+    "saliva",
+    "lips",
+    "uvula",
+    "half-closed_eyes",
+    "close-up"
   ]
 }