feat(git-sync): per-space 'Enable Git sync' toggle (Phase C, §7.1)

UI opt-in for git-sync, mirroring the existing sharing/comments settings pattern
(no new endpoint, no new mechanism; orchestrator read query untouched):
- UpdateSpaceDto.gitSyncEnabled?: boolean.
- SpaceRepo.updateGitSyncSettings: jsonb-merge into settings.gitSync.<key>
  (COALESCE || jsonb_build_object — never clobbers sibling sharing/comments);
  stored as a real jsonb boolean so the orchestrator's
  settings->'gitSync'->>'enabled' = 'true' matches.
- SpaceService.updateSpace handles the flag (audit diff) via the existing
  CASL-guarded space update path (Manage/Settings).
- client: Switch in edit-space-form (optimistic mutate + revert-on-error,
  readOnly-aware) + space types + 2 i18n keys.
- space.service.spec extended (calls updateGitSyncSettings; no-op when undefined).
tsc clean (server+client); jest src/core/space 4 pass.

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

apps/server/src/database/repos/space/space.repo.ts

@@ -111,6 +111,28 @@ export class SpaceRepo {
       .executeTakeFirst();
   }
 
+  async updateGitSyncSettings(
+    spaceId: string,
+    workspaceId: string,
+    prefKey: string,
+    prefValue: string | boolean,
+    trx?: KyselyTransaction,
+  ) {
+    const db = dbOrTx(this.db, trx);
+    return db
+      .updateTable('spaces')
+      .set({
+        settings: sql`COALESCE(settings, '{}'::jsonb)
+          || jsonb_build_object('gitSync', COALESCE(settings->'gitSync', '{}'::jsonb)
+          || jsonb_build_object('${sql.raw(prefKey)}', ${sql.lit(prefValue)}))`,
+        updatedAt: new Date(),
+      })
+      .where('id', '=', spaceId)
+      .where('workspaceId', '=', workspaceId)
+      .returningAll()
+      .executeTakeFirst();
+  }
+
   async updateCommentSettings(
     spaceId: string,
     workspaceId: string,