Add some QoL improvements to `Installation` admin

- [ ] Search by:
  - Installation ID
  - Account name (from data JSON)
  - App slug
- [ ] Add list filters for:
  - Status (Active/Inactive)
  - Account type (Organization/User)
- [ ] Add more fields to list table:
  - Account name
  - Account type badge/icon
  - Repository count
  - App slug
- [ ] Refresh installation data from GitHub?
- [ ] View related repositories inline in change form view