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-timeline.tsx

@@ -23,6 +23,8 @@ interface TimelineEvent {
   action: string;
   description: string;
   userId: string | null;
+  /** Resolved display name (server-side join). Falls back to userId when null. */
+  userName?: string | null;
   createdAt: string;
   metadata: Record<string, unknown>;
 }
@@ -56,10 +58,14 @@ function eventIcon(event: TimelineEvent) {
   return <Pencil className="h-4 w-4 text-muted-foreground" />;
 }
 
-function actorLabel(userId: string | null): string | null {
-  if (!userId) return null;
-  if (userId === 'system') return 'system';
-  return userId;
+function actorLabel(event: TimelineEvent): string | null {
+  if (event.userName) return event.userName;
+  if (!event.userId) return null;
+  if (event.userId === 'system') return 'system';
+  // Last-resort fallback when the user row was deleted: show a short token
+  // instead of a 36-char UUID. The server-side join is authoritative; this
+  // path should be rare in practice.
+  return 'a teammate';
 }
 
 export function InterestTimeline({ interestId }: InterestTimelineProps) {
@@ -100,7 +106,7 @@ export function InterestTimeline({ interestId }: InterestTimelineProps) {
       <div className="absolute left-4 top-2 bottom-2 w-px bg-border" />
 
       {events.map((event) => {
-        const actor = actorLabel(event.userId);
+        const actor = actorLabel(event);
         const isAuto = event.userId === 'system';
         return (
           <div key={event.id} className="relative flex gap-4 pb-6">