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/glory_wall_stuck_illustrious.json

@@ -2,34 +2,32 @@
   "action_id": "glory_wall_stuck_illustrious",
   "action_name": "Glory Wall Stuck Illustrious",
   "action": {
-    "full_body": "character stuck in wall, bent over pose, viewed from behind, lower body exposed",
-    "head": "head through hole, hidden inside wall",
-    "eyes": "not visible",
-    "arms": "arms through hole, reaching forward or bracing against the other side",
-    "hands": "not visible",
-    "torso": "upper torso obscured by wall, bent forward 90 degrees",
-    "pelvis": "hips trapped in hole, stuck fast, protruding rear",
-    "legs": "standing, legs spread apart, knees slightly bent for stability",
-    "feet": "standing on ground, possibly on tiptoes",
-    "additional": "wooden or concrete wall, circular hole, sense of entrapment, struggling"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "stuck, bent_over, from_behind",
+    "head": "looking_back, looking_at_viewer",
+    "eyes": "looking_at_viewer",
+    "arms": "arms_behind_back",
+    "hands": "hands_on_wall",
+    "torso": "bent_over",
+    "pelvis": "ass, ass_focus, panties, underwear, pussy",
+    "legs": "legs_up, standing",
+    "feet": "barefoot, shoes",
+    "additional": "glory_hole, wall"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/Glory_Wall_Stuck_illustrious.safetensors",
     "lora_weight": 1.0,
-    "lora_triggers": "Glory_Wall_Stuck_illustrious"
+    "lora_triggers": "glory_wall_stuck"
   },
   "tags": [
-    "stuck in wall",
-    "glory hole",
-    "bent over",
-    "from behind",
-    "trapped",
-    "lower body",
-    "legs apart",
-    "stuck"
+    "stuck",
+    "glory_hole",
+    "ass_focus",
+    "from_behind",
+    "looking_back",
+    "bent_over",
+    "ass",
+    "panties",
+    "legs_up",
+    "wall"
   ]
 }