Accounting: rename bill_approvals.vendor_name→approver_name + COA import dialog

Rename the bill_approvals approver column from vendor_name to approver_name
across UI, hooks, types, and buildium-sync. Add a Chart of Accounts import
dialog (XLSX upload + column mapping + type-alias normalization) and a
"denied" status color.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

supabase/functions/buildium-sync/index.ts

@@ -2225,7 +2225,7 @@ Deno.serve(async (req) => {
             const { error: aErr } = await supabase.from("bill_approvals").insert({
               bill_id: finalBillId,
               association_id: assocLocalId,
-              vendor_name: buildiumVendor?.Name || buildiumVendor?.CompanyName || "Buildium Vendor",
+              approver_name: buildiumVendor?.Name || buildiumVendor?.CompanyName || "Buildium Vendor",
               amount,
               status: "pending",
             });