feat(dashboard): remove Global Credentials page and listAll endpoint

[aaight]

Summary

• Remove the superadmin-only Global Credentials page at /global/credentials (no use case for seeing credentials across all organizations)
• Remove the credentials.listAll tRPC endpoint and listAllCredentials repository function since they have no consumers
• Clean up showOrg prop and organization column from CredentialsTable component
• Remove stale listAll query invalidations from credential form dialog and credentials table

Changes

• Deleted web/src/routes/global/credentials.tsx — removes GlobalCredentialsPage and route definition
• Modified web/src/routes/route-tree.ts — removed globalCredentialsRoute import and from route tree
• Modified web/src/components/layout/sidebar.tsx — removed "Global Credentials" entry from globalNav
• Modified web/src/components/settings/credentials-table.tsx — removed showOrg prop, orgName field, org column, and listAll cache invalidation
• Modified web/src/components/settings/credential-form-dialog.tsx — removed listAll cache invalidation
• Modified src/api/routers/credentials.ts — removed listAll procedure and superAdminProcedure import
• Modified src/db/repositories/credentialsRepository.ts — removed listAllCredentials function, section comment, and organizations schema import

Test plan

• tests/unit/api/routers/credentials.test.ts — all 18 tests pass (list, create, update, delete, verifyGithubIdentity)
• npm run typecheck — zero errors
• npm run lint — zero errors

Trello card: https://trello.com/c/QuL0UZIU/316-lets-remove-global-credentials-feature-from-dashboard-ui-there-is-no-usecase-for-superadmin-to-see-credentials-of-all-organizati

🤖 Generated with Claude Code

[nhopeatall]

LGTM — Clean removal of the unused Global Credentials feature. All references (route, sidebar entry, tRPC endpoint, repository function, showOrg prop, listAll cache invalidations) are fully cleaned up with no dangling imports or dead code left behind. CI is green.