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/masturbation_h.json

@@ -2,36 +2,34 @@
   "action_id": "masturbation_h",
   "action_name": "Masturbation H",
   "action": {
-    "full_body": "lying on back, body arched in pleasure, intimate perspective",
-    "head": "tilted back, flushed face, mouth open, heavy breathing, tongue out, salivating",
-    "eyes": "half-closed eyes, rolled back, heart pupils, tearing up",
-    "arms": "one arm across chest, other reaching down between legs",
-    "hands": "fondling breasts, rubbing clitoris, fingering, fingers inserted",
-    "torso": "sweaty skin, heaving chest, arched back",
-    "pelvis": "lifted hips, exposed crotch",
-    "legs": "spread legs, m-legs, knees bent, thighs open",
-    "feet": "toes curled, plantar flexion",
-    "additional": "pussy juice, messy sheets, unbuttoned clothes, intense pleasure"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "Lying on back or stomach, masturbating",
+    "head": "Heavy breathing, open mouth, blushing, head tilted back",
+    "eyes": "Eyes closed or rolling back",
+    "arms": "Grabbing own breasts or reaching downwards",
+    "hands": "Fingering pussy or squeezing breasts",
+    "torso": "Nude, arched back, shiny skin",
+    "pelvis": "Exposed pussy, pussy juice",
+    "legs": "Spread legs, open wide, knees bent",
+    "feet": "Toes curled",
+    "additional": "Top-down view, intense pleasure, sweat"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/masturbation_h.safetensors",
-    "lora_weight": 1.0,
-    "lora_triggers": "masturbation_h"
+    "lora_weight": 0.8,
+    "lora_triggers": "female masturbation, top down bottom up"
   },
   "tags": [
-    "masturbation",
-    "fingering",
+    "female_masturbation",
+    "top-down_bottom-up",
+    "lying",
+    "on_back",
     "spread_legs",
+    "nude",
+    "pussy",
+    "pussy_juice",
+    "heavy_breathing",
     "arched_back",
-    "ahegao",
-    "sweat",
-    "blush",
-    "lying_on_bed",
-    "nipple_tweak",
-    "sex_act"
+    "open_mouth",
+    "blush"
   ]
 }