refactor(forges): route device-flow revoke-access hint through the adapter

[afonsojramos]

Summary

Follow-up to #2874. The "revoke Gitify's access at GitHub → Developer Settings" hint in LoginWithDeviceFlow synthesized a fake Account ({ hostname: GITHUB_HOSTNAME, method: 'GitHub App' }) and shoved it through openAccountSettings. The label was hardcoded "GitHub" and the URL was reconstructed via account-settings dispatch rather than declared by the adapter directly.

• Add getDeviceFlowRevokeAccessUrl?(hostname): Link to ForgeAdapter.
• GitHub adapter returns the developer-settings URL.
• LoginWithDeviceFlow now uses adapter.displayName for the label and opens the adapter-provided URL. The whole hint hides when the adapter doesn't expose one — defensive against future non-GitHub forges that may register a device-flow route.

Test plan

• `pnpm exec tsc --noEmit` — clean
• `pnpm lint` — clean
• `pnpm exec vitest --run src/renderer/routes/LoginWithDeviceFlow.test.tsx src/renderer/utils/forges/github/adapter.test.ts` — passes

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
90.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[setchy]

even for GHES users

Device code flow isn't supported by GHES...

[afonsojramos]

Ah 🙊

[afonsojramos]

Closing and merging with the suggested work in #2887