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/multipleviews.json

@@ -2,34 +2,33 @@
   "action_id": "multipleviews",
   "action_name": "Multipleviews",
   "action": {
-    "full_body": "character sheet layout displaying the same character from multiple angles (front, side, back), standing pose",
-    "head": "neutral expression, face forward (front view), profile (side view)",
-    "eyes": "looking straight ahead",
-    "arms": "arms at sides, slight A-pose to show details",
-    "hands": "relaxed at sides",
-    "torso": "upright, various angles",
-    "pelvis": "facing front, side, and back",
-    "legs": "standing straight, shoulder width apart",
-    "feet": "standing flat",
-    "additional": "simple background, concept art style, turnaround, split view"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "multiple_views, on_stomach, doggystyle",
+    "head": "naughty_face, blush, open_mouth",
+    "eyes": "rolling_eyes, heart-shaped_pupils",
+    "arms": "arms_tied, grabbing_sheets",
+    "hands": "on_bed",
+    "torso": "cum_on_body, sweaty, arched_back",
+    "pelvis": "sex_from_behind, vaginal",
+    "legs": "kneeling, spread_legs",
+    "feet": "toes_curled",
+    "additional": "collage, after_sex, cumdrip, orgasm, deepthroat"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/multipleviews.safetensors",
     "lora_weight": 1.0,
-    "lora_triggers": "multipleviews"
+    "lora_triggers": "multiple_views"
   },
   "tags": [
-    "multiple views",
-    "character sheet",
-    "reference sheet",
-    "turnaround",
-    "front view",
-    "side view",
-    "back view",
-    "concept art"
+    "multiple_views",
+    "1girl",
+    "1boy",
+    "sex_from_behind",
+    "on_stomach",
+    "naughty_face",
+    "cumdrip",
+    "after_sex",
+    "orgasm",
+    "deepthroat",
+    "vaginal"
   ]
 }