fix(tickets): fix permissions toast, board fallback, assignment search, remove load more

- list_resources: return [] on PSAError instead of 502 — stops global interceptor
  toast when CW API key lacks ticket members permission (Lesson 111)
- list_boards/list_priorities: add warning logging so Railway logs reveal the
  root cause when CW permissions are missing
- TicketsPage: derive board options from ticket search results when listBoards
  returns empty (CW permissions fallback)
- TicketFilterBar: replace assignment <select> with searchable member picker —
  fixed options (All/Mine/Unassigned) + text-filtered member dropdown
- TicketQueue: remove Load More / infinite scroll; page now exists at /tickets

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/pages/TicketsPage.tsx

@@ -81,6 +81,15 @@ export default function TicketsPage() {
       })
       setTickets(result.items)
       setTotal(result.total)
+      // If the boards API returned empty (CW permissions), derive available boards from ticket data
+      setBoards(prev => {
+        if (prev.length > 0) return prev
+        const seen = new Map<number, string>()
+        result.items.forEach(t => {
+          if (t.board_id && t.board_name) seen.set(t.board_id, t.board_name)
+        })
+        return seen.size > 0 ? Array.from(seen, ([id, name]) => ({ id, name })) : prev
+      })
     } catch {
       setTickets([])
       setTotal(0)