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/testiclesucking.json

@@ -2,34 +2,31 @@
   "action_id": "testiclesucking",
   "action_name": "Testiclesucking",
   "action": {
-    "full_body": "kneeling pose, head positioned between partner's legs",
-    "head": "face nestled against scrotum, mouth engaged with testicles, neck crane upwards",
-    "eyes": "looking up or closed in concentration, eye contact with partner",
-    "arms": "reaching forward to stabilize",
-    "hands": "cupping the scrotum gently or holding partner's thighs",
-    "torso": "leaning forward, slight arch in back",
-    "pelvis": "kneeling, hips resting on heels or raised slightly",
-    "legs": "kneels on floor or bed",
-    "feet": "relaxed",
-    "additional": "saliva strings, tongue extended, cheek bulge, sucking action"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "kneeling, testicle_sucking",
+    "head": "naughty_face, blushing, tongue_out",
+    "eyes": "looking_at_viewer",
+    "arms": "arms_up",
+    "hands": "holding_penis",
+    "torso": "leaning_forward",
+    "pelvis": "kneeling",
+    "legs": "kneeling",
+    "feet": "barefoot",
+    "additional": "penis, testicles, penis_on_face, saliva_trail, huge_penis"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/testiclesucking.safetensors",
     "lora_weight": 1.0,
-    "lora_triggers": "testiclesucking"
+    "lora_triggers": "testicle sucking, balls sucking"
   },
   "tags": [
-    "testicle sucking",
-    "ball worship",
-    "oral sex",
-    "fellatio",
-    "kneeling",
-    "saliva",
-    "balls",
-    "scrotum"
+    "testicle_sucking",
+    "penis_on_face",
+    "penis",
+    "testicles",
+    "saliva_trail",
+    "naughty_face",
+    "blushing",
+    "tongue",
+    "kneeling"
   ]
 }