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/flaccid_after_cum_illustrious_000009.json

@@ -2,33 +2,31 @@
   "action_id": "flaccid_after_cum_illustrious_000009",
   "action_name": "Flaccid After Cum Illustrious 000009",
   "action": {
-    "full_body": "lying on back, limp pose, completely spent, relaxed muscles, spread eagle",
-    "head": "head tilted back, mouth open, tongue hanging out, messy hair, heavy breathing",
-    "eyes": "half-closed eyes, eyes rolled back, glassy eyes, ahegao",
-    "arms": "arms spread wide, limp arms, resting on surface",
-    "hands": "loosely open hands, twitching fingers",
-    "torso": "heaving chest, sweating skin, relaxed abdomen",
-    "pelvis": "exposed, hips flat on surface",
-    "legs": "legs spread wide, m-legs, knees bent and falling outward",
-    "feet": "toes curled",
-    "additional": "covered in white liquid, messy body, bodily fluids, after sex, exhaustion, sweat drops"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "exhausted post-coital slump, relaxing",
+    "head": "flushed face, head tilted back, disheveled hair",
+    "eyes": "half-closed, ahegao or glazed expression",
+    "arms": "limp, resting at sides",
+    "hands": "relaxed, open",
+    "torso": "sweaty skin, heaving chest",
+    "pelvis": "flaccid penis exposed, soft, seminal fluid leaking",
+    "legs": "spread wide, relaxed",
+    "feet": "loose",
+    "additional": "messy bed sheets, heavy breathing, steamy atmosphere"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/Flaccid_After_Cum_Illustrious-000009.safetensors",
     "lora_weight": 1.0,
-    "lora_triggers": "Flaccid_After_Cum_Illustrious-000009"
+    "lora_triggers": "flaccid after cum"
   },
   "tags": [
-    "lying",
+    "after_sex",
+    "flaccid",
+    "cum_in_pussy",
     "sweat",
-    "blush",
-    "open mouth",
-    "bodily fluids",
-    "spread legs",
-    "ahegao"
+    "heavy_breathing",
+    "messy_hair",
+    "cum_on_body",
+    "cum_in_mouth",
+    "after_fellatio"
   ]
 }