feat(260717-v6c): add POST /api/phishing/campaigns/[id]/mark-accidental-report route

Mirrors mark-false-positive route exactly (requirePermission phishing/approve,
UUID validation, optional reason body, campaign-existence check, 409/400/500
error mapping) but calls markCampaignAccidentalReport and returns the richer
result including notePosted/noteError.

app/api/phishing/campaigns/[id]/mark-accidental-report/route.ts

@@ -0,0 +1,83 @@
+/**
+ * POST /api/phishing/campaigns/[id]/mark-accidental-report
+ *
+ * Marks a campaign as an accidental report — an employee flagged a
+ * legitimate email by mistake. Gated by phishing/approve (same elevated
+ * tier as mark-false-positive; no separate action key). Validates the
+ * campaign id as a UUID, optionally accepts a JSON body with a `reason`
+ * string, and delegates to `markCampaignAccidentalReport`, which guards
+ * against marking a campaign that already has approved/completed
+ * remediation (RemediationConflictError -> 409). Unlike mark-false-positive,
+ * this also posts a customer-facing "reviewed, no action needed" note to
+ * every reporting employee's ticket — the response includes
+ * notePosted/noteError so the caller can distinguish full success from
+ * status-changed-but-note-failed.
+ */
+
+import { NextRequest, NextResponse } from 'next/server';
+import { requirePermission } from '@/lib/auth-utils';
+import postgresClient from '@/lib/services/postgres-client';
+import {
+  markCampaignAccidentalReport,
+  RemediationValidationError,
+  RemediationConflictError,
+} from '@/lib/services/remediation-service';
+
+const UUID_RE = /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/i;
+
+export async function POST(
+  request: NextRequest,
+  { params }: { params: Promise<{ id: string }> }
+) {
+  const { session, error } = await requirePermission('phishing', 'approve');
+  if (error) return error;
+
+  const { id } = await params;
+  // Validate UUID shape before querying — a malformed id would otherwise
+  // surface as an unhandled Postgres error -> uncaught 500.
+  if (!UUID_RE.test(id)) {
+    return NextResponse.json({ error: 'Invalid campaign id' }, { status: 400 });
+  }
+
+  // Body is optional — tolerate an empty/absent body (default reason undefined).
+  let reason: string | undefined;
+  const rawBody = await request.text();
+  if (rawBody.trim().length > 0) {
+    try {
+      const parsed = JSON.parse(rawBody) as { reason?: unknown };
+      reason = typeof parsed.reason === 'string' ? parsed.reason : undefined;
+    } catch {
+      return NextResponse.json({ error: 'Invalid JSON body' }, { status: 400 });
+    }
+  }
+
+  const actor = (session?.user as { email?: string } | undefined)?.email ?? null;
+
+  try {
+    const campaignRes = await postgresClient.query<{ id: string }>(
+      `SELECT id FROM campaigns WHERE id = $1`,
+      [id]
+    );
+    if (!campaignRes.rows[0]) {
+      return NextResponse.json({ error: 'Campaign not found' }, { status: 404 });
+    }
+
+    const result = await markCampaignAccidentalReport(id, actor, reason);
+    return NextResponse.json(result);
+  } catch (err) {
+    if (err instanceof RemediationConflictError) {
+      return NextResponse.json({ error: err.message }, { status: 409 });
+    }
+    if (err instanceof RemediationValidationError) {
+      return NextResponse.json({ error: err.message }, { status: 400 });
+    }
+    console.error('[PHISHING-MARK-ACCIDENTAL] Failed to mark campaign as accidental report', id, err);
+    return NextResponse.json(
+      {
+        error: 'Failed to mark campaign as accidental report',
+        message: err instanceof Error ? err.message : 'Unknown error',
+      },
+      { status: 500 }
+    );
+  }
+}