fix(uat-batch-2): external-EOI five-bug bundle (a/b/c/d) + presign filename override

Tackles the linked B4 #5 findings on the external-EOI flow. Item (e)
[Edit metadata affordance per row] is deferred to a later wave so it
can share infra with the broader signing-flow rework.

- (a) lying toast: uploadExternallySignedEoi now returns
  { stageChanged, newStage }. Client toasts conditionally so a
  Reservation+ deal that uploads paper-signing evidence no longer
  claims the stage advanced.
- (b) View downloads instead of previewing: SignedPdfActions takes an
  onView callback; InterestEoiTab lifts a single FilePreviewDialog and
  passes the callback down. Click-View opens the in-app preview rather
  than the presigned URL (which the storage backend served as
  attachment).
- (c) UUID filename on download: getDownloadUrl now passes the
  canonical filename through presignDownloadUrl; S3 backend adds a
  response-content-disposition override (filename + UTF-8 filename*)
  to the presign. Filesystem backend already passed it through.
- (d) Discarded dateEoiSigned: external-eoi service splits document-
  metadata writes (always — dateEoiSigned, eoiStatus='signed') from
  stage advance (gated on past-EOI). Also fires
  evaluateRule('eoi_signed') so berth-rules stay in sync when an EOI
  is filed manually.
- Default title for external-EOI dialog now derives
  "External EOI — <Client> — <berth range> — <date>" via the existing
  formatBerthRange helper; rep can override.

tsc clean. 1419/1419 vitest pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/storage/s3.ts

@@ -293,7 +293,27 @@ export class S3Backend implements StorageBackend {
 
   async presignDownload(key: string, opts: PresignOpts): Promise<{ url: string; expiresAt: Date }> {
     const expiry = opts.expirySeconds ?? 900;
-    const url = await this.client.presignedGetObject(this.bucket, key, expiry);
+    // Pass response-header overrides to minio-js's reqParams so the
+    // browser sees the original filename / content-type instead of the
+    // storage-key UUID. Without this every signed download lands with
+    // a bare UUID and no extension. Filenames are escaped per RFC 5987
+    // so a name like "Étude.pdf" survives the round-trip.
+    const reqParams: Record<string, string> = {};
+    if (opts.filename) {
+      const ascii = opts.filename.replace(/[^\x20-\x7e]/g, '_');
+      const encoded = encodeURIComponent(opts.filename);
+      reqParams['response-content-disposition'] =
+        `attachment; filename="${ascii}"; filename*=UTF-8''${encoded}`;
+    }
+    if (opts.contentType) {
+      reqParams['response-content-type'] = opts.contentType;
+    }
+    const url = await this.client.presignedGetObject(
+      this.bucket,
+      key,
+      expiry,
+      Object.keys(reqParams).length > 0 ? reqParams : undefined,
+    );
     return { url, expiresAt: new Date(Date.now() + expiry * 1000) };
   }