fix: AVIF sidecar crash, edit-metadata silent no-op, passport batch blank images, color-palette hex overflow, OCR log noise

- Convert all AI bridge inputs to PNG before writing to disk so PIL can
  read AVIF/WebP/TIFF (7 bridge files; face-detection and OCR already
  had this pattern)
- Add title/author aliases to edit-metadata schema so common field names
  actually write EXIF tags instead of being silently stripped by Zod
- Port extend/pad crop logic from passport-photo single endpoint to the
  batch pipeline so crop regions extending beyond the image get filled
  with background color instead of producing all-white output
- Clamp quantized color channels to 255 in color-palette to prevent
  Math.round(255/16)*16=256 from producing invalid hex like #100100100
- Compare OCR fallback warning against expected engine name per tier
  instead of comparing engine name against tier name (always mismatch)

apps/api/src/routes/tools/edit-metadata.ts

@@ -17,6 +17,8 @@ import { createWorkspace } from "../../lib/workspace.js";
 import { registerToolProcessFn } from "../tool-factory.js";
 
 const settingsSchema = z.object({
+  title: z.string().optional(),
+  author: z.string().optional(),
   artist: z.string().optional(),
   copyright: z.string().optional(),
   imageDescription: z.string().optional(),