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/carwashv2.json

@@ -2,36 +2,35 @@
   "action_id": "carwashv2",
   "action_name": "Carwashv2",
   "action": {
-    "full_body": "leaning forward, bending over car hood, dynamic scrubbing pose, wet body",
-    "head": "looking at viewer, smiling, wet hair sticking to face",
-    "eyes": "open, energetic, happy",
-    "arms": "stretched forward, one arm scrubbing, active motion",
-    "hands": "holding large yellow sponge, covered in soap suds",
-    "torso": "bent at waist, leaning forward, arched back, wet clothes clinging",
-    "pelvis": "hips pushed back, tilted",
-    "legs": "straddling or standing wide for stability",
-    "feet": "planted on wet pavement",
-    "additional": "soap bubbles, heavy foam on body and car, water splashing, car background"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "washing_vehicle, standing, bending_over",
+    "head": "wet_hair",
+    "eyes": "looking_at_viewer",
+    "arms": "reaching, arms_up",
+    "hands": "holding_sponge, holding_hose",
+    "torso": "wet_clothes, breast_press, breasts_on_glass",
+    "pelvis": "shorts, denim_shorts",
+    "legs": "standing, legs_apart",
+    "feet": "barefoot",
+    "additional": "car, motor_vehicle, soap_bubbles, outdoors, car_interior"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/CarWashV2.safetensors",
-    "lora_weight": 1.0,
-    "lora_triggers": "CarWashV2"
+    "lora_weight": 0.8,
+    "lora_triggers": "w4sh1n, w4sh0ut"
   },
   "tags": [
-    "car wash",
-    "holding sponge",
-    "leaning forward",
-    "bending over",
+    "car",
+    "motor_vehicle",
+    "washing_vehicle",
+    "soap_bubbles",
     "wet",
-    "wet clothes",
-    "foam",
-    "bubbles",
-    "soapy water",
-    "scrubbing"
+    "wet_hair",
+    "wet_clothes",
+    "holding_sponge",
+    "holding_hose",
+    "breasts_on_glass",
+    "breast_press",
+    "outdoors",
+    "car_interior"
   ]
 }