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/ffm_threesome___kiss_and_fellatio_illustrious.json

@@ -2,37 +2,37 @@
   "action_id": "ffm_threesome___kiss_and_fellatio_illustrious",
   "action_name": "Ffm Threesome Kiss And Fellatio Illustrious",
   "action": {
-    "full_body": "FFM threesome composition, 1boy between 2girls, simultaneous sexual activity",
-    "head": "one female kissing the male deep french kiss, second female bobbing head at crotch level",
-    "eyes": "eyes closed in pleasure, half-lidded, rolling back",
-    "arms": "wrapping around neck, holding head, bracing on thighs",
-    "hands": "fingers tangled in hair, holding penis, guiding head, groping",
-    "torso": "leaning forward, arched back, sitting upright",
-    "pelvis": "kneeling, sitting on lap, hips thrust forward",
-    "legs": "kneeling, spread legs, wrapped around waist",
-    "feet": "arched feet, curled toes",
-    "additional": "saliva trail, tongue, penis in mouth, cheek poking, blush, sweat, intimate lighting"
-  },
-  "participants": {
-    "solo_focus": "false",
-    "orientation": "FFM"
+    "full_body": "ffm_threesome, 2girls, 1boy, group_sex, sandwich_position",
+    "head": "kissing, sucking, head_grab",
+    "eyes": "closed_eyes, looking_at_partner",
+    "arms": "arms_around_neck, holding_penis, hand_on_head",
+    "hands": "stroking",
+    "torso": "leaning_forward, physical_contact",
+    "pelvis": "sitting, straddling",
+    "legs": "kneeling, spread_legs",
+    "feet": "barefoot",
+    "additional": "indoor, couch, faceless_male, saliva, blush"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/FFM_threesome_-_Kiss_and_Fellatio_Illustrious.safetensors",
     "lora_weight": 1.0,
-    "lora_triggers": "FFM_threesome_-_Kiss_and_Fellatio_Illustrious"
+    "lora_triggers": "ffm_threesome_kiss_and_fellatio"
   },
   "tags": [
-    "ffm",
-    "threesome",
-    "group sex",
-    "kissing",
-    "fellatio",
-    "blowjob",
     "2girls",
     "1boy",
-    "simultaneous oral",
-    "french kiss",
-    "penis in mouth"
+    "ffm_threesome",
+    "group_sex",
+    "hetero",
+    "kissing",
+    "fellatio",
+    "faceless_male",
+    "sitting",
+    "couch",
+    "indoor",
+    "nude",
+    "blush",
+    "saliva",
+    "sandwich_position"
   ]
 }