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/midis_expressivelanguagelovingit_v0_5_il_.json

@@ -2,34 +2,32 @@
   "action_id": "midis_expressivelanguagelovingit_v0_5_il_",
   "action_name": "Midis Expressivelanguagelovingit V0 5 Il ",
   "action": {
-    "full_body": "character displaying intense affection, leaning forward enthusiastically",
-    "head": "tilted slightly to the side, huge smile, blushing cheeks",
-    "eyes": "closed happy eyes (><) or heart-shaped pupils",
-    "arms": "brought together in front of the chest or face",
-    "hands": "fingers curved to form a heart shape (heart hands)",
-    "torso": "facing viewer, upper body focus",
-    "pelvis": "neutral",
-    "legs": "standing or obscured",
-    "feet": "obscured",
-    "additional": "floating pink hearts, sparkles, radiating happiness"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "doggystyle",
+    "head": "facing_away, moaning, heavy_breathing, sweat",
+    "eyes": "half-closed_eyes",
+    "arms": "leaning_forward",
+    "hands": "on_surface",
+    "torso": "bent_over, arched_back",
+    "pelvis": "lifted",
+    "legs": "kneeling, spread_legs",
+    "feet": "toes_curled",
+    "additional": "speech_bubble, english_text, sound_effects, motion_lines"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/midis_ExpressiveLanguageLovingit_V0.5[IL].safetensors",
     "lora_weight": 1.0,
-    "lora_triggers": "midis_ExpressiveLanguageLovingit_V0.5[IL]"
+    "lora_triggers": "lovingit"
   },
   "tags": [
-    "heart hands",
-    "hands forming heart",
-    "love",
-    "smile",
-    "blush",
-    "closed eyes",
-    "happy",
-    "adoration"
+    "lovingit",
+    "speech_bubble",
+    "moaning",
+    "english_text",
+    "doggystyle",
+    "bent_over",
+    "facing_away",
+    "sex",
+    "motion_lines",
+    "sound_effects"
   ]
 }