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_onbackoral_v0_4_il_.json

@@ -2,33 +2,31 @@
   "action_id": "midis_onbackoral_v0_4_il_",
   "action_name": "Midis Onbackoral V0 4 Il ",
   "action": {
-    "full_body": "lying on back, supine position, sensual pose",
-    "head": "head resting on surface, head tilted back, blush",
-    "eyes": "rolling eyes, eyes closed, or looking down",
-    "arms": "arms at sides, grabbing bedsheets, or arms above head",
-    "hands": "clenched hands, fingers curling",
-    "torso": "arched back, chest upward",
-    "pelvis": "hips lifted, pelvis exposed",
-    "legs": "spread legs, legs apart, knees bent, m-legs, open legs",
-    "feet": "toes curled, feet in air",
-    "additional": "pov, view from above, between legs, bed, messy sheets"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "lying, on_back, sitting_on_person",
+    "head": "open_mouth, head_back, looking_up",
+    "eyes": "closed_eyes, half_closed_eyes",
+    "arms": "arms_at_sides, arms_above_head",
+    "hands": "clenched_hands",
+    "torso": "chest, breasts, lying_on_back",
+    "pelvis": "lying",
+    "legs": "legs_straight, legs_apart",
+    "feet": "toes_curled",
+    "additional": "irrumatio, fellatio, sitting_on_breasts, sitting_on_chest, struggling"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/midis_OnBackOral_V0.4[IL].safetensors",
     "lora_weight": 1.0,
-    "lora_triggers": "midis_OnBackOral_V0.4[IL]"
+    "lora_triggers": "oral, lying"
   },
   "tags": [
-    "lying on back",
-    "spread legs",
-    "pov",
-    "legs apart",
-    "supine",
-    "m-legs",
-    "sensual"
+    "lying",
+    "on_back",
+    "oral",
+    "irrumatio",
+    "fellatio",
+    "sitting_on_person",
+    "sitting_on_breasts",
+    "sitting_on_chest",
+    "struggling"
   ]
 }