fix(ui): humanize enum labels, format dates, resolve actor names, loading skeleton

- Documents hub signer status now renders via a label map (`Pending`,
  `Signed`, `Declined`, …) instead of the raw lowercase enum value.
- Invoice detail formats `dueDate` and `paymentDate` as `MMM d, yyyy`
  via `date-fns` instead of leaking raw `2025-03-14` ISO strings, and
  swaps the "Payment Method" free-text input for a `Select` of labelled
  options (`Bank transfer`, `Credit card`, …) so we never store
  `bank_transfer` from a hand-typed field again.
- Interest tabs `MilestoneSection` status badge uses a `humanizeStatus`
  helper so values like `waiting_for_signatures` show as
  `Waiting For Signatures` (correctly title-cased) instead of being a
  lower-snake-case fragment inside an ALL-CAPS pill.
- `OUTCOME_BADGE` in the interest header now has a fall-through that
  renders any unknown outcome as a closed-state badge, preventing a
  closed interest from looking open just because its enum was added
  upstream without a matching label entry.
- Interest timeline route joins the `user` table and returns
  `userName` alongside `userId`; the client renders the resolved name
  instead of a 36-char UUID. Falls back to `'a teammate'` if the user
  row was deleted.
- Invoice "New / Step 3 — Review" replaces the truncated UUID display
  with a server-resolved client/company name via a small `useQuery`,
  so users can confirm they picked the right billing entity before
  submitting.
- New `loading.tsx` for client detail renders a header / tab strip /
  card skeleton during the server-component / initial-query window
  that previously flashed empty.

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

src/components/interests/interest-tabs.tsx

@@ -26,6 +26,12 @@ const LEAD_CATEGORY_OPTIONS = LEAD_CATEGORIES.map((c) => ({
   label: c.replace(/_/g, ' ').replace(/\b\w/g, (m) => m.toUpperCase()),
 }));
 
+// Convert raw enum values like `waiting_for_signatures` → `Waiting For Signatures`.
+function humanizeStatus(value: string | null): string | null {
+  if (!value) return null;
+  return value.replace(/_/g, ' ').replace(/\b\w/g, (m) => m.toUpperCase());
+}
+
 interface InterestTabsOptions {
   interestId: string;
   currentUserId?: string;
@@ -203,7 +209,7 @@ function MilestoneSection({
         </div>
         {status ? (
           <span className="rounded-full bg-muted px-2 py-0.5 text-[10px] font-medium uppercase tracking-wide text-muted-foreground">
-            {status.replace(/_/g, ' ')}
+            {humanizeStatus(status)}
           </span>
         ) : null}
       </header>