Decompose the remaining God Components into hooks, helpers and sub-components

FE6: split the oversized page and panel components into thin layout shells plus colocated use<Component> hooks, .constants.ts, .helpers.ts (with tests) and presentational sub-components, following the established 'logic in a hook, render in slices' pattern. Behaviour, markup, classes and effect order are unchanged. Largest reductions: PackingListPanel 1598->42, FileManager 1055->36, AdminPage 1525->167, BudgetPanel 1266->146, JourneyDetailPage 2822->547, PlacesSidebar 945->66, CollabChat 861->106, CollabNotes 1417->532. DayPlanSidebar's drag-and-drop render body was left intact (ref-identity sensitive) and only its toolbar/modals/constants were extracted.

client/src/components/Collab/CollabChatMessageText.tsx

@@ -0,0 +1,21 @@
+import { URL_REGEX } from './CollabChat.constants'
+
+/* ── Message Text with clickable URLs ── */
+interface MessageTextProps {
+  text: string
+}
+
+export function MessageText({ text }: MessageTextProps) {
+  const parts = text.split(URL_REGEX)
+  const urls = text.match(URL_REGEX) || []
+  const result = []
+  parts.forEach((part, i) => {
+    if (part) result.push(part)
+    if (urls[i]) result.push(
+      <a key={i} href={urls[i]} target="_blank" rel="noopener noreferrer" style={{ color: 'inherit', textDecoration: 'underline', textUnderlineOffset: 2, opacity: 0.85 }}>
+        {urls[i]}
+      </a>
+    )
+  })
+  return <>{result}</>
+}