fix(dashboard): mobile keyboard scroll lock, auto-reload hash, ChatView snap

- Add useMobileScrollLock hook using position:fixed body lock (Bootstrap/
  Headless UI/Stripe pattern) to prevent iOS Safari from shifting the
  document and visualViewport when an input inside a fixed-position modal
  is focused. Wire into 15 input-bearing modals plus ChatView, replacing
  ChatView's inline body-overflow effect.
- Widen computeBuildVersion in vite.config.ts to hash the entire app/ tree
  so the version-check poll actually notices rebuilds (FN-3333 follow-up;
  previously only main.tsx and package.json were hashed).
- ChatView: on input blur, suppress keyboard-aware sizing for 450ms while
  reserving mobile-nav-bar space, so the composer snaps to its final
  height in one move instead of crawling down with iOS's keyboard slide
  and then jumping again when the nav bar reappears.

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

packages/dashboard/app/components/MilestoneSliceInterviewModal.tsx

@@ -29,6 +29,7 @@ import {
 import { ConversationHistory } from "./ConversationHistory";
 import { useSessionLock } from "../hooks/useSessionLock";
 import { useAiSessionSync } from "../hooks/useAiSessionSync";
+import { useMobileScrollLock } from "../hooks/useMobileScrollLock";
 import { getSessionTabId } from "../utils/getSessionTabId";
 
 interface MilestoneSliceInterviewModalProps {
@@ -73,6 +74,7 @@ export function MilestoneSliceInterviewModal({
   projectId,
   resumeSessionId,
 }: MilestoneSliceInterviewModalProps) {
+  useMobileScrollLock(isOpen);
   const [view, setView] = useState<ViewState>({ type: "initial" });
   const [error, setError] = useState<string | null>(null);
   const [responseHistory, setResponseHistory] = useState<QuestionResponse[]>([]);