Fix GitHub repo list failing to load on slow installations

[midigofrank]

Description

Fixes a captured error on /projects/:id/settings where the GitHub sync section fails to load repos list when one of a user's GitHub installations takes >5s to return its repos.

By default, Task.async_stream has a timeout of 5 secs, this PR bumps it up to 30 secs

Closes #4810

Validation steps

1. Existing version-control test suite still passes:
   mix test test/lightning_web/live/project_live_test.exs:4132
2. To reproduce the original bug locally, add a Process.sleep(5005) inside
   the Task.async_stream callback in
   lib/lightning_web/live/project_live/github_sync_component.ex on main
   and open the project settings page — the GitHub section shows the
   failure state. With this fix the section loads (slow installations are
   dropped).
3. The existing Stream.filter(&match?({:ok, _}, &1)) was meant to drop failed tasks but only works under on_timeout: :kill_task. This PR sets that, plus a 30s per-task timeout, so slow installations are dropped and the rest of the user's installations and repos still render.

Additional notes for the reviewer

1. No test was added for the timeout itself — exercising the new 30s threshold
   in a test would make it slow and flaky. The existing 30-test version-control
   suite covers the happy path.
2. The inner pagination call (maybe_fetch_remaining_repos) already uses
   timeout: :infinity, so a single installation's full repo fetch can easily
   exceed 5s. 30s on the outer task is a generous but bounded upper limit.

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  (e.g., :owner, :admin, :editor, :viewer)
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[github-actions]

The change is a 6-line operational fix: adds timeout: 30_000 and on_timeout: :kill_task options to a Task.async_stream/2 call that fetches GitHub repos per installation, plus a CHANGELOG entry. No database queries, no new web events, no resource mutations.

Security Review ✅

• S0 (project scoping): N/A, the change only adjusts Task.async_stream timeout options on an outbound GitHub API call; no project-scoped queries or params are touched.
• S1 (authorization): N/A, no new LiveView events, controller actions, or policy decisions introduced.
• S2 (audit trail): N/A, no config-resource writes — the diff is read-only repo-fetching plus a CHANGELOG entry.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.2%. Comparing base (4e910ec) to head (02da4c6).

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #4811     +/-   ##
=======================================
- Coverage   90.3%   90.2%   -0.1%     
=======================================
  Files        442     442             
  Lines      22543   22543             
=======================================
- Hits       20350   20337     -13     
- Misses      2193    2206     +13     

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