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/cum_shot.json

@@ -2,35 +2,42 @@
   "action_id": "cum_shot",
   "action_name": "Cum Shot",
   "action": {
-    "full_body": "close-up, portrait, upper body focus, kneeling or sitting",
-    "head": "mouth open, tongue out, blushing, sweating, cum on face, cum in mouth, semen on hair, messy hair",
-    "eyes": "half-closed eyes, rolling eyes, heart-shaped pupils, looking at viewer, glazed eyes",
-    "arms": "arms relaxed or hands framing face",
-    "hands": "hands on cheeks, making peace sign, or wiping face",
-    "torso": "exposed upper body, wet skin, cleavage",
-    "pelvis": "obscured or out of frame",
-    "legs": "kneeling or out of frame",
+    "full_body": "portrait or upper body focus, capturing the moment of ejaculation or aftermath",
+    "head": "tilted back or facing forward, expression of pleasure or shock",
+    "eyes": "closed or rolling back, eyelashes detailed",
+    "arms": "out of frame or hands touching face",
+    "hands": "optional, touching face or wiping",
+    "torso": "chest visible, potentially with cum_on_body",
+    "pelvis": "usually out of frame in this context",
+    "legs": "out of frame",
     "feet": "out of frame",
-    "additional": "white liquid, splashing, sticky texture, aftermath, detailed fluids, high contrast"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "additional": "white fluids, messy, dripping, shiny skin"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/cum_shot.safetensors",
-    "lora_weight": 1.0,
-    "lora_triggers": "cum_shot"
+    "lora_weight": 0.8,
+    "lora_triggers": "cum, facial, ejaculation"
   },
   "tags": [
-    "cum_shot",
-    "facial",
-    "semen",
     "cum",
+    "facial",
+    "ejaculation",
+    "cum_on_body",
+    "cum_on_breasts",
+    "cum_in_eye",
+    "cum_in_mouth",
     "bukkake",
-    "aftermath",
-    "nsfw",
-    "liquid",
-    "messy"
+    "after_sex",
+    "messy_body",
+    "sticky",
+    "white_fluid",
+    "open_mouth",
+    "tongue",
+    "bukkake",
+    "tongue_out",
+    "saliva",
+    "sweat",
+    "blush",
+    "ahegao"
   ]
 }