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/two_handed_handjob.json

@@ -2,33 +2,33 @@
   "action_id": "two_handed_handjob",
   "action_name": "Two Handed Handjob",
   "action": {
-    "full_body": "kneeling or sitting close to partner, leaning forward",
-    "head": "tilted down watching hands or looking up with eye contact",
-    "eyes": "focused on the action or lustful gaze",
-    "arms": "extended forward, active engagement",
-    "hands": "both hands wrapped around penis, double grip, milking motion, tight hold, one hand above the other",
-    "torso": "leaning in towards partner's groin",
-    "pelvis": "positioned for stability",
-    "legs": "kneeling or spread",
-    "feet": "tucked or resting",
-    "additional": "erection, glans, stimulation, nsfw"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "two-handed_handjob",
+    "head": "naughty_face, blush, seductive_smile",
+    "eyes": "looking_at_viewer, half-closed_eyes",
+    "arms": "arms_forward",
+    "hands": "penis_grab, two_hands",
+    "torso": "breasts",
+    "pelvis": "penis",
+    "legs": "spread_legs",
+    "feet": "",
+    "additional": "glansjob, motion_lines, steam, sound_effects, pov"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/two-handed_handjob.safetensors",
-    "lora_weight": 1.0,
-    "lora_triggers": "two-handed_handjob"
+    "lora_weight": 0.9,
+    "lora_triggers": "two-handed_handjobV1, glansjob, two-handed_handjob"
   },
   "tags": [
-    "handjob",
-    "two hands",
-    "double grip",
-    "penis",
-    "stimulation",
-    "nsfw",
-    "stroking"
+    "two-handed_handjob",
+    "glansjob",
+    "penis_grab",
+    "naughty_face",
+    "seductive_smile",
+    "motion_lines",
+    "steam",
+    "sound_effects",
+    "looking_at_viewer",
+    "half-closed_eyes",
+    "handjob"
   ]
 }