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/srjxia.json

@@ -2,31 +2,31 @@
   "action_id": "srjxia",
   "action_name": "Srjxia",
   "action": {
-    "full_body": "standing, leaning on object, leaning on sword, confident pose, solo",
-    "head": "looking at viewer, arrogant expression, slight head tilt",
-    "eyes": "purple eyes, narrow gaze",
-    "arms": "one hand on hip, one hand holding sword handle",
-    "hands": "resting on sword hilt, hand on hip",
-    "torso": "straight posture, slight twist",
-    "pelvis": "weight shifted to one leg",
-    "legs": "crossed legs or standing relaxedly",
-    "feet": "standing on ground",
-    "additional": "giant sword, claymore, weapon, embers, magma, fire particles"
-  },
-  "participants": {
-    "solo_focus": "true",
-    "orientation": "MF"
+    "full_body": "minigirl sitting inside a glass jar",
+    "head": "looking at viewer",
+    "eyes": "open eyes",
+    "arms": "arms close to body, cramped space",
+    "hands": "hands on legs or pressing against glass",
+    "torso": "leaning forward or upright",
+    "pelvis": "sitting on bottom of jar",
+    "legs": "knees directly up, knees to chest",
+    "feet": "bare feet or shoeless",
+    "additional": "transparent glass, reflection, confined space"
   },
   "lora": {
     "lora_name": "Illustrious/Poses/srjxia.safetensors",
     "lora_weight": 1.0,
-    "lora_triggers": "srjxia"
+    "lora_triggers": "GirlInGlassJar"
   },
   "tags": [
-    "arknights",
-    "character focus",
-    "demon girl",
-    "weapon focus",
-    "anime style"
+    "minigirl",
+    "jar",
+    "glass",
+    "in_container",
+    "sitting",
+    "knees_to_chest",
+    "stuck",
+    "cramped",
+    "trapped"
   ]
 }