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/cooperativepaizuri.json

@@ -2,35 +2,32 @@
   "action_id": "cooperativepaizuri",
   "action_name": "Cooperativepaizuri",
   "action": {
-    "full_body": "intimate sexual pose, two people interacting closely",
-    "head": "flushed face, drooling, tongue out, expression of pleasure or submission",
-    "eyes": "half-closed eyes, looking down, ahegao or heart-shaped pupils",
-    "arms": "arms supporting body weight or holding partner",
-    "hands": "recipient's hands grasping subject's breasts, squeezing breasts together towards center",
-    "torso": "exposed breasts, heavy cleavage, chest compressed by external hands",
-    "pelvis": "leaning forward, hips raised or straddling",
-    "legs": "kneeling, spread legs, or wrapping around partner",
-    "feet": "arched feet, toes curled",
-    "additional": "penis sliding between breasts, friction, lubrication, skin indentation"
-  },
-  "participants": {
-    "solo_focus": "false",
-    "orientation": "MFF"
+    "full_body": "cooperative_paizuri, 2girls, 1boy, sexual_activity",
+    "head": "smile, open_mouth, facial",
+    "eyes": "looking_at_partner, half_closed_eyes",
+    "arms": "arms_around_neck, grabbing_penis",
+    "hands": "on_penis, guiding_penis",
+    "torso": "large_breasts, breasts_touching, nipples",
+    "pelvis": "penis, glans, erection",
+    "legs": "kneeling, straddling",
+    "feet": "barefoot",
+    "additional": "pov, cum_on_body, fluids"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/cooperativepaizuri.safetensors",
     "lora_weight": 1.0,
-    "lora_triggers": "cooperativepaizuri"
+    "lora_triggers": "cooperative paizuri"
   },
   "tags": [
+    "cooperative_paizuri",
+    "2girls",
+    "1boy",
     "paizuri",
-    "assisted paizuri",
-    "male hand",
-    "breast squeeze",
-    "titjob",
-    "penis between breasts",
-    "sexual act",
-    "cleavage",
-    "big breasts"
+    "breasts",
+    "penis",
+    "facial",
+    "pov",
+    "from_side",
+    "large_breasts"
   ]
 }