feat(enhance): LoRA switches per template (#218)

A template can offer optional LoRAs the app turns on or off.

- enhance.toml: [[template.lora]] { id, label, default } per template.
  Each id drives every workflow node titled `imageapi:lora:<id>`, so
  Wan's high- and low-noise pair share one switch.
- POST /enhance takes `loras: {id: bool}`; a missing id uses its default,
  an id the template doesn't offer is a 400. Off sets strength_model
  (and strength_clip when present) to 0, so the graph is never rewired.
- The resolved switches are stored on the job (new enhance_jobs.loras
  JSON column) and returned in the job view, so a retry or adjust can
  repeat them; GET /enhance/templates lists each template's switches.
- A lora-titled node without a declaration keeps its exported strength,
  and a declaration without nodes isn't offered; both are startup
  warnings. A lora-titled node without a numeric strength_model fails
  the template.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/enhance/service.rs

@@ -292,6 +292,7 @@ impl EnhanceService {
         template_name: &str,
         prompt: Option<&str>,
         reference: Option<&SourceFile>,
+        loras: &std::collections::BTreeMap<String, bool>,
     ) -> Result<EnhanceJobRow, EnhanceError> {
         let Some(client) = &self.client else {
             return Err(EnhanceError::Disabled);
@@ -319,7 +320,13 @@ impl EnhanceService {
             None => None,
         };
         let filled = template
-            .fill(&source, prompt, reference_path.as_deref(), &mut random_seed)
+            .fill(
+                &source,
+                prompt,
+                reference_path.as_deref(),
+                loras,
+                &mut random_seed,
+            )
             .map_err(|e| EnhanceError::BadRequest(e.0))?;
 
         if !self.probe_now().await {
@@ -365,6 +372,8 @@ impl EnhanceService {
             created_at: now,
             updated_at: now,
             run_ms: None,
+            loras: (!filled.loras.is_empty())
+                .then(|| serde_json::to_string(&filled.loras).unwrap_or_default()),
         };
         self.dao
             .lock()