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>

migrations/2026-11-03-100000_add_enhance_loras/down.sql

@@ -0,0 +1 @@
+ALTER TABLE enhance_jobs DROP COLUMN loras;

migrations/2026-11-03-100000_add_enhance_loras/up.sql

@@ -0,0 +1,2 @@
+-- The job's resolved LoRA switches (#218): JSON {id: bool}; NULL = the template had none.
+ALTER TABLE enhance_jobs ADD COLUMN loras TEXT;