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/deepthroat_ponytailhandle_anime_il_v1.json

@@ -2,39 +2,32 @@
   "action_id": "deepthroat_ponytailhandle_anime_il_v1",
   "action_name": "Deepthroat Ponytailhandle Anime Il V1",
   "action": {
-    "full_body": "kneeling, performing deepthroat fellatio, body angled towards partner",
-    "head": "tilted back forcedly, mouth stretched wide, gagging, face flushed, hair pulled taught",
-    "eyes": "tearing up, rolled back, looking up, streaming tears",
-    "arms": "reaching forward, holding onto partner's legs for support",
-    "hands": "grasping thighs, fingers digging in",
-    "torso": "leaning forward, back slightly arched",
-    "pelvis": "kneeling position",
-    "legs": "knees on ground, shins flat",
-    "feet": "toes curled tightly",
-    "additional": "saliva trails, heavy breathing, hand grabbing ponytail, penis in mouth, irrumatio"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "irrumatio, fellatio, 1boy, 1girl, duo",
+    "head": "forced_oral, head_back, mouth_open, saliva, drooling",
+    "eyes": "crying, tears, glare, wide_eyes",
+    "arms": "arms_at_sides",
+    "hands": "hands_down",
+    "torso": "upper_body",
+    "pelvis": "n/a",
+    "legs": "n/a",
+    "feet": "n/a",
+    "additional": "grabbing_another's_hair, penis, deepthroat, ponytail"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/Deepthroat_PonytailHandle_Anime_IL_V1.safetensors",
     "lora_weight": 1.0,
-    "lora_triggers": "Deepthroat_PonytailHandle_Anime_IL_V1"
+    "lora_triggers": "deepthroat_ponytailhandle, grabbing another's hair, ponytail"
   },
   "tags": [
+    "irrumatio",
     "deepthroat",
     "fellatio",
-    "oral sex",
-    "hair pull",
-    "grabbing hair",
+    "grabbing_another's_hair",
     "ponytail",
-    "kneeling",
-    "gagging",
-    "irrumatio",
+    "drooling",
     "tears",
-    "saliva",
-    "submissive",
-    "forced oral"
+    "crying",
+    "penis",
+    "forced"
   ]
 }