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/stealthfellatio.json

@@ -2,36 +2,33 @@
   "action_id": "stealthfellatio",
   "action_name": "Stealthfellatio",
   "action": {
-    "full_body": "duo, one person sitting at a table or desk, the other person hiding underneath performing oral sex, split composition showing above and below surface",
-    "head": "receiver looking ahead trying to maintain composure, giver's head positioned at crotch level",
-    "eyes": "nervous glance, looking away, or rolled back in pleasure",
-    "arms": "resting casually on the table top or gripping the edge of the desk tightly",
-    "hands": "hands folded on table or clutching thighs",
-    "torso": "receiver sitting upright, giver crouched or bent over",
-    "pelvis": "sexual contact, fellatio, penis in mouth",
-    "legs": "receiver legs spread, giver kneeling between legs",
-    "feet": "flat on floor",
-    "additional": "under the table, secret sex, public setting, tablecloth, cutaway view, risk of getting caught"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "kneeling, sitting, under_table, from_side",
+    "head": "fellatio, irrumatio, deepthroat",
+    "eyes": "looking_up",
+    "arms": "penis_hold, hands_on_lap",
+    "hands": "holding_penis",
+    "torso": "leaning_forward",
+    "pelvis": "kneeling",
+    "legs": "kneeling",
+    "feet": "tucked",
+    "additional": "desk, stealth_sex, floor, office"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/stealthfellatio.safetensors",
     "lora_weight": 1.0,
-    "lora_triggers": "stealthfellatio"
+    "lora_triggers": "stealth fellatio, under table"
   },
   "tags": [
-    "stealth",
+    "stealth_fellatio",
     "under_table",
+    "desk",
+    "stealth_sex",
     "fellatio",
-    "blowjob",
-    "public_sex",
-    "secret_sex",
-    "under_desk",
-    "flustered",
-    "duo",
-    "table_hiding"
+    "irrumatio",
+    "kneeling",
+    "from_side",
+    "penis_hold",
+    "floor",
+    "deepthroat"
   ]
 }