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/panty_aside_illustrious_v1_0.json

@@ -2,31 +2,28 @@
   "action_id": "panty_aside_illustrious_v1_0",
   "action_name": "Panty Aside Illustrious V1 0",
   "action": {
-    "full_body": "pulling panties aside, revealing pose, front view, standing or lying on back",
-    "head": "looking at viewer, blush, embarrassed or seductive expression",
-    "eyes": "eye contact, alluring gaze",
-    "arms": "arms reaching down, arm at side",
-    "hands": "hand on hip, fingers hooking panties, pulling fabric, thumb inside waistband",
-    "torso": "bare midriff, navel, exposed slightly",
-    "pelvis": "panties, underwear, hip bone, side tie, exposed hip, gap",
-    "legs": "thighs, bare legs, slightly parted",
-    "feet": "standing or feet out of frame",
-    "additional": "lingerie, teasing, skin indentation, exposure"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "panties_aside",
+    "head": "looking_at_viewer",
+    "eyes": "ultra-detailed-eyes",
+    "arms": "arms_at_sides",
+    "hands": "adjusting_panties",
+    "torso": "cute_girl",
+    "pelvis": "panties_aside, panties, pussy",
+    "legs": "legs_apart",
+    "feet": "standing",
+    "additional": "censored"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/panty aside_illustrious_V1.0.safetensors",
-    "lora_weight": 1.0,
-    "lora_triggers": "panty aside_illustrious_V1.0"
+    "lora_weight": 0.7,
+    "lora_triggers": "panties aside, panties, pussy"
   },
   "tags": [
-    "panty aside",
-    "pulling panties aside",
-    "underwear",
-    "lingerie",
-    "teasing"
+    "panties_aside",
+    "panties",
+    "pussy",
+    "adjusting_panties",
+    "legs_apart",
+    "censored"
   ]
 }