Hide bounty management actions from unauthorized viewers

[Robertg761]

Summary

• hide bounty Edit Amount/Delete controls unless the current org role can manage bounties
• add LiveView coverage for logged-out viewers, non-member viewers, and org moderators

Fixes #238.

Verification

• mix deps.get
• mix format --check-formatted lib/algora_web/live/org/bounties_live.ex test/algora_web/live/org/bounties_live_test.exs
• git diff --check
• MIX_ENV=test mix test test/algora_web/live/org/bounties_live_test.exs blocked before tests ran because TEST_DATABASE_URL is unset and the test repo config has no fallback :database key in this environment. The app and dependencies compiled before hitting the DB config error.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}