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/ballsdeep_il_v2_2_s.json

@@ -2,33 +2,29 @@
   "action_id": "ballsdeep_il_v2_2_s",
   "action_name": "Ballsdeep Il V2 2 S",
   "action": {
-    "full_body": "intense sexual intercourse, intimate close-up on genital connection, visceral physical interaction",
-    "head": "flushed face, expression of intense pleasure, head thrown back, mouth slightly open, panting",
-    "eyes": "eyes rolling back, ahegao or tightly closed eyes, heavy breathing",
-    "arms": "muscular arms tensed, holding partner's hips firmly, veins visible",
-    "hands": "hands gripping waist or buttocks, fingers digging into skin, pulling partner closer",
-    "torso": "sweaty skin, arched back, abdominal muscles engaged",
-    "pelvis": "hips slammed forward, testicles pressed firmly against partner's skin, complete insertion",
-    "legs": "thighs interlocking, kneeling or legs wrapped around partner's waist",
-    "feet": "toes curled tightly",
-    "additional": "sex, vaginal, balls deep, motion blur on hips, bodily fluids, skin indentation, anatomical focus"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "sexual intercourse, variable position (prone, girl on top, or from behind)",
+    "head": "expression of intensity or pleasure, often looking back or face down",
+    "eyes": "rolled back or squeezed shut",
+    "arms": "grasping sheets or holding partner",
+    "hands": "clenched or grabbing",
+    "torso": "arched or pressed against contrasting surface",
+    "pelvis": "hips pushed firmly against partner's hips, joined genitals",
+    "legs": "spread wide or wrapped around partner",
+    "feet": "toes curled",
+    "additional": "deep penetration, testicles pressed flat against skin, stomach bulge visible"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/BallsDeep-IL-V2.2-S.safetensors",
     "lora_weight": 1.0,
-    "lora_triggers": "BallsDeep-IL-V2.2-S"
+    "lora_triggers": "deep penetration"
   },
   "tags": [
-    "nsfw",
+    "deep_penetration",
+    "testicles",
+    "stomach_bulge",
     "sex",
+    "anal",
     "vaginal",
-    "internal view",
-    "cross-section",
-    "deep penetration",
-    "mating press"
+    "gaping"
   ]
 }