fix: verbose error handling, batch processing, and multi-file support

- Replace [object Object] errors with readable messages across all 20+ API
  routes by normalizing Zod validation errors to strings (formatZodErrors)
- Add parseApiError() on frontend to defensively handle any details type
- Add global Fastify error handler with full stack traces in logs
- Fix image-to-pdf auth: Object.entries(headers) → headers.forEach()
- Fix passport-photo: safeParse + formatZodErrors, safe error extraction
- Fix OCR silent fallbacks: log exception type/message when falling back,
  include actual engine used in API response and Docker logs
- Fix split tool: process all uploaded images, combine into ZIP with
  subfolders per image
- Fix batch support for blur-faces, strip-metadata, edit-metadata,
  vectorize: add processAllFiles branch for multi-file uploads
- Docker: LOG_LEVEL=debug, PYTHONWARNINGS=default for visibility
- Add Playwright e2e tests verifying all fixes against Docker container

apps/api/src/routes/pipeline.ts

@@ -17,6 +17,7 @@ import { z } from "zod";
 import { env } from "../config.js";
 import { db, schema } from "../db/index.js";
 import { autoOrient } from "../lib/auto-orient.js";
+import { formatZodErrors } from "../lib/errors.js";
 import { validateImageBuffer } from "../lib/file-validation.js";
 import { sanitizeFilename } from "../lib/filename.js";
 import { decodeHeic } from "../lib/heic-converter.js";
@@ -130,10 +131,7 @@ export async function registerPipelineRoutes(app: FastifyInstance): Promise<void
       if (!result.success) {
         return reply.status(400).send({
           error: "Invalid pipeline definition",
-          details: result.error.issues.map((i) => ({
-            path: i.path.join("."),
-            message: i.message,
-          })),
+          details: formatZodErrors(result.error.issues),
         });
       }
       pipeline = result.data;
@@ -431,10 +429,7 @@ export async function registerPipelineRoutes(app: FastifyInstance): Promise<void
       if (!result.success) {
         return reply.status(400).send({
           error: "Invalid pipeline definition",
-          details: result.error.issues.map((i) => ({
-            path: i.path.join("."),
-            message: i.message,
-          })),
+          details: formatZodErrors(result.error.issues),
         });
       }
       pipeline = result.data;