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/reversefellatio.json

@@ -2,34 +2,33 @@
   "action_id": "reversefellatio",
   "action_name": "Reversefellatio",
   "action": {
-    "full_body": "lying supine on a surface (bed/couch), body flat, head positioned over the edge",
-    "head": "inverted, hanging upside down, neck hyper-extended and exposed, hair hanging down due to gravity",
-    "eyes": "looking up (inverted) or rolled back, expressive",
-    "arms": "resting alongside the head or reaching back to hold the edge",
-    "hands": "gripping sheets or relaxed",
-    "torso": "lying flat on back, chest facing up, slightly arched",
-    "pelvis": "resting flat on the surface",
-    "legs": "extended straight or knees bent with feet on the surface",
-    "feet": "resting on the surface",
-    "additional": "gravity effects on hair and clothing, inverted perspective, often implies receiving oral sex from above/behind"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "1girl and 1boy in sexual position, one partner upside-down",
+    "head": "head_back, mouth connection",
+    "eyes": "eyes_closed",
+    "arms": "arms_supporting_body or grabbing_hips",
+    "hands": "on_thighs",
+    "torso": "inverted torso alignment",
+    "pelvis": "hips aligned for oral interaction",
+    "legs": "legs_up or straddling",
+    "feet": "bare_feet or shoes",
+    "additional": "deepthroat, throat_bulge, sexual_act"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/reversefellatio.safetensors",
     "lora_weight": 1.0,
-    "lora_triggers": "reversefellatio"
+    "lora_triggers": "reverse fellatio, upside-down, upside-down fellatio"
   },
   "tags": [
-    "reverse fellatio",
+    "reverse_fellatio",
     "upside-down",
-    "head hanging off bed",
-    "lying on back",
-    "supine",
-    "neck exposed",
-    "inverted face",
-    "from above"
+    "fellatio",
+    "irrumatio",
+    "deepthroat",
+    "throat_bulge",
+    "head_back",
+    "from_side",
+    "penis",
+    "1girl",
+    "1boy"
   ]
 }