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/imminent_penetration_illustriousxl_lora_nochekaiser.json

@@ -2,36 +2,31 @@
   "action_id": "imminent_penetration_illustriousxl_lora_nochekaiser",
   "action_name": "Imminent Penetration Illustriousxl Lora Nochekaiser",
   "action": {
-    "full_body": "lying on back, intimate close-up, sexual activity, extreme proximity to viewer",
-    "head": "heavily blushing, panting, mouth open, sweat, expression of anticipation or arousal",
-    "eyes": "half-closed eyes, upturned eyes, looking at viewer",
-    "arms": "reaching out or clutching bedsheets",
-    "hands": "hands gripping, knuckles white",
-    "torso": "arched back, heaving chest",
-    "pelvis": "hips lifted, genitals exposed, genital contact",
-    "legs": "spread legs, m-legs, knees up, legs apart",
-    "feet": "toes curled",
-    "additional": "imminent penetration, penis tip, touching, just the tip, friction, pov, insertion validation"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "imminent_penetration, lying, on_back, spread_legs",
+    "head": "blush, closed_mouth",
+    "eyes": "looking_at_viewer",
+    "arms": "arms_at_sides",
+    "hands": "torso_grab",
+    "torso": "navel, open_shirt, open_clothes",
+    "pelvis": "bottomless, heterosexual, imminent_vaginal",
+    "legs": "spread_legs, panties_around_one_leg",
+    "feet": "feet_out_of_frame",
+    "additional": "sex, penis, erection, uncensored"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/imminent-penetration-illustriousxl-lora-nochekaiser.safetensors",
     "lora_weight": 1.0,
-    "lora_triggers": "imminent-penetration-illustriousxl-lora-nochekaiser"
+    "lora_triggers": "imminent penetration, torso grab, imminent vaginal, panties around one leg"
   },
   "tags": [
-    "imminent penetration",
-    "tip",
-    "touching",
-    "pov",
-    "sex",
-    "spread legs",
+    "imminent_penetration",
+    "torso_grab",
+    "lying",
+    "on_back",
+    "spread_legs",
+    "bottomless",
+    "open_shirt",
     "blush",
-    "sweat",
-    "genital close-up",
-    "nsfw"
+    "panties_around_one_leg"
   ]
 }