Security hardening from 2026-07-01 audit

- Exclude supabase/ from Docker build context (leaked service_role key file)
- /api/files: exact per-user namespace match + reject path traversal;
  storage resolveKey rejects ".."/"." segments (fixes cross-user file read)
- Add ownsProperty/Unit/Tenant checks to tenants, maintenance (landlord path),
  and documents (JSON branch, now field-whitelisted) create handlers
- Escape user data in follow-up + payment-link emails (reuse escapeHtml)
- Neutralize CSV formula injection in toCsv + export routes
- Tighter sign-in rate limit (10/min); env-gated email verification + sender
- Per-request nonce CSP; drop script-src 'unsafe-inline' (styles unchanged)
- Add input length bounds; validate follow-ups POST body

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/api/export/tenants/route.ts

@@ -3,6 +3,7 @@ import { asc, eq } from "drizzle-orm"
 import { db } from "@/lib/db"
 import { tenants } from "@/lib/db/schema"
 import { getSessionUser } from "@/lib/session"
+import { toCsv } from "@/lib/db/admin-queries"
 
 export async function GET() {
   const user = await getSessionUser()
@@ -17,23 +18,20 @@ export async function GET() {
     orderBy: asc(tenants.last_name),
   })
 
-  const headers = ["First Name", "Last Name", "Email", "Phone", "Property", "Unit", "Status", "Move In Date", "Notes"]
-  const lines = [
-    headers.join(","),
-    ...rows.map((t) => [
-      `"${t.first_name ?? ""}"`,
-      `"${t.last_name ?? ""}"`,
-      `"${t.email ?? ""}"`,
-      `"${t.phone ?? ""}"`,
-      `"${t.property?.name ?? ""}"`,
-      `"${t.unit?.unit_number ?? ""}"`,
+  const csv = toCsv(
+    ["First Name", "Last Name", "Email", "Phone", "Property", "Unit", "Status", "Move In Date", "Notes"],
+    rows.map((t) => [
+      t.first_name ?? "",
+      t.last_name ?? "",
+      t.email ?? "",
+      t.phone ?? "",
+      t.property?.name ?? "",
+      t.unit?.unit_number ?? "",
       t.status ?? "",
       t.move_in_date ?? "",
-      `"${(t.notes ?? "").replace(/"/g, "'")}"`,
-    ].join(","))
-  ]
-
-  const csv = lines.join("\n")
+      t.notes ?? "",
+    ])
+  )
 
   return new NextResponse(csv, {
     headers: {