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/kissing_penis_illustriousxl_lora_nochekaiser.json

@@ -2,33 +2,30 @@
   "action_id": "kissing_penis_illustriousxl_lora_nochekaiser",
   "action_name": "Kissing Penis Illustriousxl Lora Nochekaiser",
   "action": {
-    "full_body": "kneeling or crouching, leaning forward towards partner's groin area",
-    "head": "face close to crotch, mouth touching or kissing the glans",
-    "eyes": "looking toward object, looking up (ahegao possible), or closed eyes",
-    "arms": "reaching forward, bent at elbows",
-    "hands": "holding the penis shaft, cupping testicles, or resting on partner's thighs",
-    "torso": "leaning forward, slight arch",
-    "pelvis": "kneeling on the ground or bed",
-    "legs": "kneeling, bent knees",
-    "feet": "toes curled or flat on surface",
-    "additional": "saliva, penis, erection, glans, sexual act, intimacy"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "fellatio, squatting, from_side",
+    "head": "profile, blush",
+    "eyes": "closed_eyes",
+    "arms": "arms_down",
+    "hands": "hands_on_legs",
+    "torso": "leaning_forward",
+    "pelvis": "squatting",
+    "legs": "squatting",
+    "feet": "barefoot",
+    "additional": "spoken_heart, heart"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/kissing-penis-illustriousxl-lora-nochekaiser.safetensors",
     "lora_weight": 1.0,
-    "lora_triggers": "kissing-penis-illustriousxl-lora-nochekaiser"
+    "lora_triggers": "kissing penis, fellatio"
   },
   "tags": [
-    "kissing penis",
+    "kissing_penis",
     "fellatio",
-    "oral sex",
-    "blowjob",
-    "penis",
-    "kneeling",
-    "nsfw"
+    "squatting",
+    "from_side",
+    "closed_eyes",
+    "blush",
+    "spoken_heart",
+    "heart"
   ]
 }