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/midis_cunnilingus_v0_6_naixl_vpred_.json

@@ -2,32 +2,30 @@
   "action_id": "midis_cunnilingus_v0_6_naixl_vpred_",
   "action_name": "Midis Cunnilingus V0 6 Naixl Vpred ",
   "action": {
-    "full_body": "duo focus, cunnilingus, oral sex, sexual act, female receiving oral sex, partner positioning between legs",
-    "head": "face buried in crotch, face between legs, tongue out, licking",
-    "eyes": "eyes closed, rolling eyes, expression of pleasure",
-    "arms": "holding thighs, gripping hips, supporting body weight",
-    "hands": "spreading labia, touching clitoris, fingering",
-    "torso": "leaning forward, prone",
-    "pelvis": "hips raised, exposed vulva, pelvic tilt",
-    "legs": "spread legs, open legs, legs over shoulders, m-legs, knees bent",
-    "feet": "toes curled, plantar flexion",
-    "additional": "pussy juice, saliva trail, wet pussy, intimacy"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "sitting_on_face, straddling, leaning_forward",
+    "head": "looking_down",
+    "eyes": "looking_at_viewer",
+    "arms": "arms_support, hands_on_own_legs",
+    "hands": "resting",
+    "torso": "leaning_forward",
+    "pelvis": "straddling, hips_spread",
+    "legs": "spread_legs, kneeling, thighs",
+    "feet": "out_of_frame",
+    "additional": "pov, from_below, intimate_perspective, aggressive_angle"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/midis_Cunnilingus_V0.6[NAIXL-vPred].safetensors",
     "lora_weight": 1.0,
-    "lora_triggers": "midis_Cunnilingus_V0.6[NAIXL-vPred]"
+    "lora_triggers": "cunnilingus pov, looking down"
   },
   "tags": [
     "cunnilingus",
-    "oral sex",
-    "pussy licking",
-    "nsfw",
-    "sexual act",
-    "duo"
+    "pov",
+    "sitting_on_face",
+    "looking_down",
+    "from_below",
+    "straddling",
+    "spread_legs",
+    "thighs"
   ]
 }