feat(send-dialog): surface per-port attachment threshold in preview UI

Per PRE-DEPLOY-PLAN § 1.3.9. Adds an informational banner to the
SendDocumentDialog explaining the size cutoff at which the attachment
switches from inline to a 24h signed-link download. Threshold sourced
from the existing `email_attach_threshold_mb` setting, plumbed through
the previewBody return shape so rep-facing dialogs don't need to call
the admin-only sales-config endpoint.

Bounce monitoring deferred to land alongside the email_bounces table
in Step 3 (schema additions).

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

src/components/shared/send-document-dialog.tsx

@@ -56,7 +56,12 @@ interface SendDocumentDialogProps {
 }
 
 interface PreviewResponse {
-  data: { html: string; markdown: string; unresolved: string[] };
+  data: {
+    html: string;
+    markdown: string;
+    unresolved: string[];
+    attachmentThresholdMb: number;
+  };
 }
 
 export function SendDocumentDialog(props: SendDocumentDialogProps) {
@@ -97,6 +102,9 @@ function SendDocumentDialogInner({
 
   // Live preview via /api/v1/document-sends/preview. Re-runs whenever the
   // body text or recipient changes (debounce-by-react-query for free).
+  // The preview also surfaces the per-port attachment-size threshold so
+  // the rep can see up-front whether their attachment will go inline vs
+  // as a 24h download link.
   const previewQuery = useQuery<PreviewResponse>({
     queryKey: [
       'document-sends-preview',
@@ -205,6 +213,13 @@ function SendDocumentDialogInner({
               </p>
             </div>
 
+            {previewQuery.data?.data.attachmentThresholdMb !== undefined && (
+              <p className="rounded border border-slate-200 bg-slate-50 px-3 py-2 text-xs text-slate-700">
+                Files over <strong>{previewQuery.data.data.attachmentThresholdMb} MB</strong> are
+                sent as a 24-hour download link instead of an inline attachment.
+              </p>
+            )}
+
             <div className="space-y-1">
               <Label htmlFor="ds-body">Message body</Label>
               <Textarea

src/lib/services/document-sends.service.ts

@@ -263,7 +263,16 @@ export async function previewBody(
   recipient: SendRecipientInput,
   customBody: string | null,
   ctx: { berthId?: string; brochureLabel?: string } = {},
-): Promise<{ html: string; markdown: string; unresolved: string[] }> {
+): Promise<{
+  html: string;
+  markdown: string;
+  unresolved: string[];
+  /** Per-port size cutoff at which the attachment is replaced with a
+   * 24-hour signed-link in the email body. Surfaced to the compose UI
+   * so the rep sees up-front whether their attachment will go inline
+   * vs as a link. */
+  attachmentThresholdMb: number;
+}> {
   const content = await getSalesContentConfig(portId);
   const template = customBody?.trim()?.length
     ? customBody
@@ -274,7 +283,12 @@ export async function previewBody(
   const expanded = expandMergeTokens(template, values);
   const unresolved = findUnresolvedTokens(template, values);
   const html = renderEmailBody(expanded);
-  return { html, markdown: expanded, unresolved };
+  return {
+    html,
+    markdown: expanded,
+    unresolved,
+    attachmentThresholdMb: content.emailAttachThresholdMb,
+  };
 }
 
 // ─── Internal helpers ────────────────────────────────────────────────────────