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/breast_pressh.json

@@ -2,33 +2,32 @@
   "action_id": "breast_pressh",
   "action_name": "Breast Pressh",
   "action": {
-    "full_body": "character pressing breasts together with hands or arms to enhance cleavage",
-    "head": "slightly tilted forward, often with a flushed or embarrassed expression",
-    "eyes": "looking down at chest or shyly at viewer",
-    "arms": "bent at elbows, brought in front of the chest",
-    "hands": "placed on the sides or underneath breasts, actively squeezing or pushing them inward",
-    "torso": "upper body leaned slightly forward or arched back to emphasize the chest area",
-    "pelvis": "neutral standing or sitting position",
-    "legs": "standing straight or sitting with knees together",
-    "feet": "planted firmly on ground if standing",
-    "additional": "emphasis on soft body physics, squish deformation, and skin indentation around the fingers"
-  },
-  "participants": {
-    "solo_focus": "false",
-    "orientation": "FF"
+    "full_body": "sandwiched, girl_sandwich, standing, height_difference, size_difference",
+    "head": "head_between_breasts, face_between_breasts, cheek_squash",
+    "eyes": "eyes_closed, squints",
+    "arms": "hugging, arms_around_waist",
+    "hands": "hands_on_back",
+    "torso": "breast_press, chest_to_chest",
+    "pelvis": "hips_touching",
+    "legs": "standing, legs_apart",
+    "feet": "barefoot",
+    "additional": "1boy, 2girls, multiple_girls, hetero"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/breast_pressH.safetensors",
-    "lora_weight": 1.0,
+    "lora_weight": 0.6,
     "lora_triggers": "breast_pressH"
   },
   "tags": [
-    "breast press",
-    "squeezing breasts",
-    "cleavage",
-    "hands on breasts",
-    "self groping",
-    "squish",
-    "upper body"
+    "height_difference",
+    "girl_sandwich",
+    "breast_press",
+    "sandwiched",
+    "size_difference",
+    "head_between_breasts",
+    "cheek_squash",
+    "face_between_breasts",
+    "1boy",
+    "2girls"
   ]
 }