[Chore] Update fixtures

[mrubens]

What changed

Follow-up to #192: replaces the remaining real-world identifiers that sweep missed in five test files with fictional placeholder data, ahead of the repo going public.

• packages/github/src/__tests__/task-run-token.test.ts: the multi-repo token test now uses ExampleOrg/example-backend / ExampleOrg/example-frontend with install-exampleorg, matching the Roomote/example-app + install-roomote convention already used by the neighboring environment test.
• apps/web/src/app/(onboarding)/setup/StepSourceControlConfig.client.test.tsx and apps/web/src/trpc/commands/github/mutations.test.ts: the GitHub organization fixture is now example-org (including the github.com/organizations/example-org/settings/apps/new manifest URL assertion).
• apps/web/src/lib/server/auth.test.ts: adoOrganization is now ado-organization, matching the descriptive placeholder style of the surrounding config (ado-client-id, ado-client-secret).
• apps/web/src/components/layout/side-nav/SideNav.client.test.tsx: the env-4 environment name is now Sandbox.

No production code changes; string literals in test fixtures only.

How it was tested

• A case-insensitive grep for the internally tracked identifier list returns zero hits on this branch.
• Targeted Vitest runs for all five affected test files pass (6 tests in @roomote/github, 38 across the four @roomote/web files).
• pnpm lint:fast and pnpm check-types:fast pass locally; Knip is green in this PR's CI.

Checklist

• The PR title follows the repo convention: [Fix], [Feat], [Improve], [Refactor], [Docs], or [Chore] followed by a user-facing description
• This PR is small and scoped to one change
• pnpm lint and pnpm check-types pass locally
• I added tests or included a clear manual validation note above
• I removed secrets, tokens, private keys, and customer data from code, logs, and screenshots
• If this change should appear in the changelog, I ran pnpm changeset (not needed: test-fixture text only)

[roomote-roomote]

No code issues found. Verified the five fixture files: each identifier swap updates both the input and its matching assertion consistently, the customer-identifier grep is clean, and the @roomote/github token test passes (6/6). See task

_{Reviewed b8e63b8}