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/giantess_missionary_000037.json

@@ -2,33 +2,32 @@
   "action_id": "giantess_missionary_000037",
   "action_name": "Giantess Missionary 000037",
   "action": {
-    "full_body": "lying on back, missionary position, legs spread, engaging in sexual activity, large female figure dominating perspective",
-    "head": "head resting on pillow, looking down at partner or looking up in pleasure",
-    "eyes": "half-closed eyes, looking at viewer, or rolled back",
-    "arms": "reaching up, wrapping around partner, or resting on surface",
-    "hands": "grasping sheets, holding partner, or open palms",
-    "torso": "chest facing up, breasts pressed or swaying",
-    "pelvis": "hips centered, groin exposed, receiving",
-    "legs": "spread legs, knees bent, legs in variable m-shape or wrapping around partner",
-    "feet": "toes curled, feet in air or resting on bed",
-    "additional": "giantess, size difference, micro male (optional context), low angle view"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "missionary, lying, on_back, size_difference, giantess, larger_female",
+    "head": "face_between_breasts, burying_face",
+    "eyes": "closed_eyes, expressionless",
+    "arms": "hug, arms_around_back",
+    "hands": "hands_on_back",
+    "torso": "breasts, cleavage, large_breasts",
+    "pelvis": "hops",
+    "legs": "spread_legs, legs_up",
+    "feet": "barefoot",
+    "additional": "male_on_top, hetero, bearhug, femdom"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/Giantess_Missionary-000037.safetensors",
-    "lora_weight": 1.0,
-    "lora_triggers": "Giantess_Missionary-000037"
+    "lora_weight": 0.9,
+    "lora_triggers": "M0t0rB0atM1ss10nary"
   },
   "tags": [
     "missionary",
     "giantess",
-    "lying on back",
-    "legs spread",
-    "size difference",
-    "sex",
-    "vaginal"
+    "size_difference",
+    "larger_female",
+    "face_between_breasts",
+    "hug",
+    "spread_legs",
+    "lying",
+    "on_back",
+    "cleavage"
   ]
 }