fix(data-app): page through GET /apps so list finds apps beyond the first page (#798)

[padak]

What

kbagent data-app list could report "No data apps found." in a project that has data apps.

DataScienceClient.list_apps() sent one GET /apps with no query params. The Data Science API paginates that collection (default page = 100 items), and the page mixes workspace deployments (keboola.sandboxes) with data apps (keboola.data-apps). The service filters client-side, so when the first 100 deployments were all workspaces the list came back empty. In the reporter's project the first data app was item #258 of 1,114.

Fix (client layer only)

• list_apps() now pages with limit / offset until it gets a short (or empty) page, and returns the full collection. Both callers (DataAppService.list_data_apps and the sync engine's data-app type lookup in services/_sync_data_app.py) get the complete list with no change on their side.
• New constants in constants.py: DATA_SCIENCE_APPS_PAGE_SIZE = 500 (the page size the reporter verified) and DATA_SCIENCE_APPS_MAX_PAGES = 200. The page cap only stops an infinite loop if a server ignores offset; hitting it logs a warning.
• The {"data": [...]} wrapped response shape is still accepted.
• Gotcha entry in gotchas.md, tagged (since vNEXT, #798). No version bump, no changelog entry.

How tested

• New pytest-httpx client tests (TestListAppsPaginationClient in tests/test_data_app_service.py):
  • a single short page sends exactly one request with limit=500&offset=0
  • a full page of sandboxes followed by a page containing data apps: those data apps are returned, and the exact limit/offset params are checked
  • an exactly-full last page is followed by one empty-page request
  • the wrapped {"data": [...]} shape works
  • the page cap stops a server that ignores offset
• A service test (TestDataAppListFiltersWorkspaces): 300 sandboxes plus 1 data app, and only the data app is listed.
• make check: 6908 passed, 15 skipped. Lint, format, ty and the doc/version gates are green.
• Not verified against a live project with more than 100 deployments.

Fixes #798