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/cunnilingus_on_back_illustriousxl_lora_nochekaiser.json

@@ -2,33 +2,36 @@
   "action_id": "cunnilingus_on_back_illustriousxl_lora_nochekaiser",
   "action_name": "Cunnilingus On Back Illustriousxl Lora Nochekaiser",
   "action": {
-    "full_body": "lying on back, receiving oral sex, partner between legs",
-    "head": "head tilted back, expression of pleasure, blushing, heavy breathing, mouth open",
-    "eyes": "eyes closed, rolling eyes, or looking down at partner",
-    "arms": "arms resting on bed or reaching towards partner",
-    "hands": "gripping bedsheets, clutching pillow, or holding partner's head",
-    "torso": "arched back, chest heaving",
-    "pelvis": "hips lifted, crotch exposed to partner",
-    "legs": "spread legs, legs apart, knees bent, m-legs",
-    "feet": "toes curled, feet on bed",
-    "additional": "partner's face in crotch, tongue, saliva, sexual act, intimate focus"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "lying, on_back, spread_legs, nude",
+    "head": "torogao, blush, sweat",
+    "eyes": "half-closed_eyes",
+    "arms": "bent_arms",
+    "hands": "hands_on_own_chest",
+    "torso": "navel, nipples, sweat",
+    "pelvis": "cunnilingus, pussy",
+    "legs": "spread_legs, thighs",
+    "feet": "",
+    "additional": "on_bed, pillow, from_side"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/cunnilingus-on-back-illustriousxl-lora-nochekaiser.safetensors",
     "lora_weight": 1.0,
-    "lora_triggers": "cunnilingus-on-back-illustriousxl-lora-nochekaiser"
+    "lora_triggers": "cunnilingus on back"
   },
   "tags": [
     "cunnilingus",
-    "oral sex",
-    "lying on back",
-    "spread legs",
-    "pleasure",
-    "sex",
-    "NSFW"
+    "lying",
+    "on_back",
+    "spread_legs",
+    "hands_on_own_chest",
+    "torogao",
+    "half-closed_eyes",
+    "sweat",
+    "blush",
+    "navel",
+    "nipples",
+    "hetero",
+    "on_bed",
+    "from_side"
   ]
 }