🔧(collaboration) make the version history granularity configurable

Version grouping used a hard-coded 60s window, and its
timestamps are minted server-side.
We now expose COLLABORATION_VERSION_GRANULARITY_MS
through /config, read it in useDocActivity.

By doing so, we can control the granularity of
version history with settings, it can be adjusted as
needed. It will help us to test different version
history granularities in our e2e tests.

src/backend/core/api/viewsets.py

@@ -2969,6 +2969,7 @@ class ConfigView(drf.views.APIView):
             "AI_FEATURE_BLOCKNOTE_ENABLED",
             "AI_FEATURE_LEGACY_ENABLED",
             "API_USERS_SEARCH_QUERY_MIN_LENGTH",
+            "COLLABORATION_VERSION_GRANULARITY_MS",
             "COLLABORATION_WS_URL",
             "COLLABORATION_WS_INACTIVITY_TIMEOUT",
             "CONVERSION_FILE_EXTENSIONS_ALLOWED",