feat(git-sync): client 'Git sync' provenance badge + git in runtime image (Phase D)

- page-history history-item: a lastUpdatedSource==='git-sync' version renders a
  neutral gray 'Git sync' badge (git-merge icon), NOT the agent badge/deep-link
  (it is not an agent edit). +2 i18n keys.
- Dockerfile: install git in the installer (runtime) stage — VaultGit shells out
  to git, so assertGitAvailable() needs the binary at runtime.
Client tsc clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/client/src/features/page-history/components/history-item.tsx

@@ -1,6 +1,7 @@
 import { Text, Group, UnstyledButton, Avatar, Tooltip } from "@mantine/core";
 import { CustomAvatar } from "@/components/ui/custom-avatar.tsx";
 import { AiAgentBadge } from "@/components/ui/ai-agent-badge.tsx";
+import { GitSyncBadge } from "@/components/ui/git-sync-badge.tsx";
 import { formattedDate } from "@/lib/time";
 import classes from "./css/history.module.css";
 import clsx from "clsx";
@@ -41,6 +42,7 @@ const HistoryItem = memo(function HistoryItem({
   const contributors = historyItem.contributors;
   const hasContributors = contributors && contributors.length > 0;
   const isAgentEdit = historyItem.lastUpdatedSource === "agent";
+  const isGitSyncEdit = historyItem.lastUpdatedSource === "git-sync";
 
   return (
     <UnstyledButton
@@ -108,6 +110,10 @@ const HistoryItem = memo(function HistoryItem({
             onActivate={() => setHistoryModalOpen(false)}
           />
         )}
+
+        {isGitSyncEdit && (
+          <GitSyncBadge authorName={historyItem.lastUpdatedBy?.name} />
+        )}
       </Group>
     </UnstyledButton>
   );