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/reclining_cowgirl_position.json

@@ -2,34 +2,32 @@
   "action_id": "reclining_cowgirl_position",
   "action_name": "Reclining Cowgirl Position",
   "action": {
-    "full_body": "reclining cowgirl pose, female on top, straddling partner, leaning backwards",
-    "head": "tilted back, neck exposed, chin up",
-    "eyes": "half-closed, rolling back, or closed in pleasure",
-    "arms": "arms extended backward, supporting upper body weight behind the torso",
-    "hands": "hands resting on partner's shins or on the bed for stability",
-    "torso": "arched back, spine curved, chest thrust forward, leaning back",
-    "pelvis": "seated on partner's hips, straddling, crotch contact",
-    "legs": "knees bent, thighs spread wide, straddling partner's torso",
-    "feet": "toes pointed, tucked under or resting on the mattress",
-    "additional": "partner lying on back underneath, intimate setting, bed sheets"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "cowgirl_position, straddling, girl_on_top, leaning_back",
+    "head": "head_back, facing_another",
+    "eyes": "half-closed_eyes",
+    "arms": "arms_extended, holding_hands, interlocked_fingers",
+    "hands": "clald_hands, interlocked_fingers",
+    "torso": "arched_back, leaning_back, bouncing_breasts",
+    "pelvis": "straddling, on_top",
+    "legs": "kneeling, spread_legs, straddling",
+    "feet": "toes_pointed",
+    "additional": "from_side, motion_lines, motion_blur"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/Reclining_Cowgirl_Position.safetensors",
-    "lora_weight": 1.0,
+    "lora_weight": 0.5,
     "lora_triggers": "Reclining_Cowgirl_Position"
   },
   "tags": [
-    "cowgirl position",
-    "sex",
-    "woman on top",
-    "leaning back",
+    "cowgirl_position",
     "straddling",
-    "arched back",
-    "erotic",
-    "vaginal sex"
+    "girl_on_top",
+    "leaning_back",
+    "holding_hands",
+    "interlocked_fingers",
+    "from_side",
+    "arched_back",
+    "half-closed_eyes",
+    "bouncing_breasts"
   ]
 }