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/fellatio_on_couch_illustriousxl_lora_nochekaiser.json

@@ -2,37 +2,36 @@
   "action_id": "fellatio_on_couch_illustriousxl_lora_nochekaiser",
   "action_name": "Fellatio On Couch Illustriousxl Lora Nochekaiser",
   "action": {
-    "full_body": "kneeling on couch, leaning forward, performing fellatio, sexual act, duo focus",
-    "head": "face in crotch, mouth open, sucking, cheeks hollowed, saliva trail",
-    "eyes": "looking up, half-closed eyes, eye contact, ahegao",
-    "arms": "reaching forward, holding partner's thighs, resting on cushions",
-    "hands": "stroking penis, gripping legs, guiding head",
-    "torso": "leaning forward, bent over, arched back",
-    "pelvis": "kneeling, hips pushed back",
-    "legs": "kneeling on sofa, spread slightly, knees bent",
-    "feet": "toes curled, resting on upholstery, plantar flexion",
-    "additional": "indoor, living room, sofa, couch, fabric texture, motion lines"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "fellatio, sitting, on_couch, hetero, oral",
+    "head": "blush, sweat, head_down",
+    "eyes": "looking_down, eyes_closed",
+    "arms": "arms_at_side",
+    "hands": "hands_on_legs",
+    "torso": "breast_press, nipples, nude, leaning_forward",
+    "pelvis": "sitting, nude",
+    "legs": "sitting, legs_apart",
+    "feet": "feet_on_floor",
+    "additional": "couch, penis, testicles, uncensored"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/fellatio-on-couch-illustriousxl-lora-nochekaiser.safetensors",
     "lora_weight": 1.0,
-    "lora_triggers": "fellatio-on-couch-illustriousxl-lora-nochekaiser"
+    "lora_triggers": "fellatio on couch, hetero, penis, oral, sitting, fellatio, testicles, blush, couch, sweat, breast press, nipples, completely nude, uncensored"
   },
   "tags": [
     "fellatio",
-    "oral sex",
-    "on couch",
-    "kneeling",
-    "sofa",
+    "on_couch",
+    "hetero",
     "penis",
-    "cum",
-    "saliva",
-    "indoor",
-    "sex",
-    "blowjob"
+    "oral",
+    "sitting",
+    "testicles",
+    "blush",
+    "sweat",
+    "breast_press",
+    "nipples",
+    "nude",
+    "uncensored",
+    "couch"
   ]
 }