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/fertilization_illustriousxl_lora_nochekaiser.json

@@ -2,34 +2,34 @@
   "action_id": "fertilization_illustriousxl_lora_nochekaiser",
   "action_name": "Fertilization Illustriousxl Lora Nochekaiser",
   "action": {
-    "full_body": "lying on back, legs spread, internal view, cross-section, x-ray view of abdomen",
-    "head": "head resting on pillow, heavy breathing, blushing",
-    "eyes": "half-closed eyes, rolled back eyes or heart-shaped pupils",
-    "arms": "arms resting at sides or holding bed sheets",
-    "hands": "hands clutching sheets or resting on stomach",
-    "torso": "exposed tummy, navel, transparent skin effect",
-    "pelvis": "focus on womb, uterus visible, internal female anatomy",
-    "legs": "legs spread wide, m-legs, knees up",
-    "feet": "toes curled",
-    "additional": "visualized fertilization process, sperm, egg, cum inside, glowing internal organs, detailed uterus, biology diagram style"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "sex, vaginal, on_bed, nude, cowboy_shot",
+    "head": "ahegao, blush, open_mouth, head_back",
+    "eyes": "rolled_eyes, half_closed_eyes",
+    "arms": "arms_at_sides",
+    "hands": "clenched_hands",
+    "torso": "nude, nipples, navel",
+    "pelvis": "pussy, cum_in_pussy, internal_cumshot, penis, hetero",
+    "legs": "spread_legs, legs_up",
+    "feet": "bare_feet",
+    "additional": "cross-section, fertilization, impregnation, uterus, ovum, sperm_cell, ovaries, ejaculation"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/fertilization-illustriousxl-lora-nochekaiser.safetensors",
     "lora_weight": 1.0,
-    "lora_triggers": "fertilization-illustriousxl-lora-nochekaiser"
+    "lora_triggers": "fertilization, ovum, impregnation, sperm cell, cross-section, cum in pussy, internal cumshot, uterus, cum, sex, vaginal, ovaries, penis, hetero, ejaculation"
   },
   "tags": [
     "fertilization",
-    "internal view",
     "cross-section",
-    "x-ray",
-    "womb",
-    "cum inside",
+    "ovum",
+    "sperm_cell",
+    "impregnation",
     "uterus",
-    "impregnation"
+    "internal_cumshot",
+    "cum_in_pussy",
+    "vaginal",
+    "ovaries",
+    "ahegao",
+    "on_bed"
   ]
 }