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/blowjobcomicpart2.json

@@ -2,34 +2,31 @@
   "action_id": "blowjobcomicpart2",
   "action_name": "Blowjobcomicpart2",
   "action": {
-    "full_body": "kneeling in front of standing partner, intimate interaction, oral sex pose",
-    "head": "tilted up, mouth open, cheek bulge, blushing, messy face",
-    "eyes": "rolled back, heart-shaped pupils, crossed eyes, or looking up",
-    "arms": "reaching forward, holding partner's legs or hips",
-    "hands": "stroking, gripping thighs, holding shaft, guiding",
-    "torso": "leaning forward, subordinate posture",
-    "pelvis": "kneeling on ground",
-    "legs": "bent at knees, shins on floor",
-    "feet": "tucked under or toes curled",
-    "additional": "saliva, slobber, motion lines, speech bubbles, sound effects, comic panel structure, greyscale or screentones"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "3koma, comic layout, vertical panel sequence",
+    "head": "tongue_out, open mouth, saliva",
+    "eyes": "empty_eyes, rolled eyes",
+    "arms": "arms_down or holding_head",
+    "hands": "fingers_on_penis",
+    "torso": "visible torso",
+    "pelvis": "sexual_activity",
+    "legs": "kneeling or sitting",
+    "feet": "out_of_frame",
+    "additional": "fellatio, irrumatio, licking_penis, ejaculation, excessive_cum"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/BlowjobComicPart2.safetensors",
     "lora_weight": 1.0,
-    "lora_triggers": "BlowjobComicPart2"
+    "lora_triggers": "bjmcut"
   },
   "tags": [
-    "nsfw",
-    "fellatio",
-    "oral sex",
-    "kneeling",
+    "3koma",
     "comic",
-    "monochrome",
-    "saliva",
-    "ahegao"
+    "fellatio",
+    "irrumatio",
+    "licking_penis",
+    "ejaculation",
+    "excessive_cum",
+    "empty_eyes",
+    "tongue_out"
   ]
 }