Add usage_caps_input slot to project settings page

[elias-ba]

Description

Adds a usage_caps_input view-extension slot at /projects/:project_id/settings, mirroring the existing concurrency_input slot pattern. Downstream apps register a component via route metadata (metadata: %{usage_caps_input: SomeComponent}) and Lightning renders it in the settings view.

Closes #4725.

Replaces the now-permanently-closed #4726 (which bundled this slot with the rejected cap-columns-on-Lightning approach from #4724). This PR keeps only the slot wiring; the cap data and cap UI live entirely in Thunderbolt's thunderbolt.project_caps table per OpenFn/thunderbolt#649.

Validation steps

1. mix test test/lightning_web/live/project_live/settings_test.exs — existing settings tests should pass unchanged.
2. With no downstream registration, the settings page renders identically to today (slot is empty).
3. Register a stub component on the route via metadata: %{usage_caps_input: SomeStub} and confirm the component renders on the settings page.

Additional notes for the reviewer

The diff is three files: settings.ex refactors the route_metadata read into a single fetch and adds the :usage_caps_input lookup; settings.html.heex renders <.live_component :if={...}> when the assign is present; CHANGELOG.md documents the slot.

AI Usage

• I have used Claude Code

Pre-submission checklist

• I have performed a self-review of my code.
• I have implemented and tested all related authorization policies. (e.g., :owner, :admin, :editor, :viewer)
• I have updated the changelog.
• I have ticked a box in "AI usage" in this PR

[github-actions]

This PR adds a usage_caps_input view-extension slot to the project settings page, mirroring the existing concurrency_input slot pattern. It's a UI-only change: the LiveView reads route metadata and conditionally renders a registered live_component (no-op for OSS by default).

Security Review ✅

• S0 (project scoping): The @project passed to the new live_component comes from the :project_scope on_mount hook (settings.ex:25), not spoofable params; no new queries are introduced.
• S1 (authorization): N/A — no new handle_event, controller action, or write operation; the slot is a view extension that hands project and current_user (settings.html.heex:243-249) to a downstream component for its own gating, mirroring the existing concurrency_input precedent.
• S2 (audit trail): N/A — no DB writes, mutations, or config-resource changes; this is purely a render-time component slot.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.95%. Comparing base (d8e1059) to head (00cfc81).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4729      +/-   ##
==========================================
+ Coverage   89.94%   89.95%   +0.01%     
==========================================
  Files         444      444              
  Lines       21979    21981       +2     
==========================================
+ Hits        19768    19772       +4     
+ Misses       2211     2209       -2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.