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/cleavageteasedwnsty_000008.json

@@ -2,35 +2,36 @@
   "action_id": "cleavageteasedwnsty_000008",
   "action_name": "Cleavageteasedwnsty 000008",
   "action": {
-    "full_body": "Medium shot or close-up focus on the upper body, character facing forward",
-    "head": "Looking directly at viewer, chin slightly tucked or tilted, expression varying from shy blush to seductive smile",
-    "eyes": "Eye contact, focused on the viewer",
-    "arms": "Elbows bent, forearms brought up towards the chest",
-    "hands": "Fingers grasping the hem of the collar or neckline of the top, pulling it downwards",
-    "torso": "Clothing fabric stretched taut, neckline pulled down low to reveal cleavage, emphasis on the chest area",
-    "pelvis": "Neutral position, often obscured in close-up shots",
-    "legs": "Neutral or out of frame",
-    "feet": "Out of frame",
-    "additional": "Fabric tension lines, revealing skin, seductive atmosphere"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "leaning_forward, sexually_suggestive",
+    "head": "looking_at_viewer, smile, blush, one_eye_closed",
+    "eyes": "blue_eyes, looking_at_viewer",
+    "arms": "arms_bent_at_elbows",
+    "hands": "hands_on_own_chest, clothes_pull, adjusting_clothes",
+    "torso": "cleavage, breasts_squeezed_together, areola_slip, bare_shoulders, collarbone",
+    "pelvis": "n/a",
+    "legs": "n/a",
+    "feet": "n/a",
+    "additional": "teasing, undressing"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/CleavageTeaseDwnsty-000008.safetensors",
     "lora_weight": 1.0,
-    "lora_triggers": "CleavageTeaseDwnsty-000008"
+    "lora_triggers": "pulling down own clothes, teasing"
   },
   "tags": [
-    "cleavage",
-    "clothes pull",
-    "collar pull",
-    "shirt pull",
-    "looking at viewer",
-    "breasts",
+    "clothes_pull",
+    "shirt_pull",
     "teasing",
+    "breasts_squeezed_together",
+    "areola_slip",
+    "undressing",
+    "leaning_forward",
+    "cleavage",
+    "hands_on_own_chest",
+    "collarbone",
+    "bare_shoulders",
+    "sexually_suggestive",
     "blush",
-    "holding clothes"
+    "one_eye_closed"
   ]
 }