R1:a65244c44918

Build a very basic subscription detail page in Phortune

Summary:
Ref T6881.

- Add a subscription detail page.

Minor cosmetics:

- Fix glyph, from "X" (old "X marks the spot" icon) to "diamond" (new gem icon).
- Name the initial account "Default Account" instead of "Personal Account", since this seems more general.

Test Plan:
{F278623}

And I got two full days to test that Jan 30/31 -> Feb 28 billing logic!

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T6881…