fix: address Docker pnpm and scope input issues

[markwylde]

Summary

• Activate pnpm through Corepack in both Docker build and runtime stages so the image can run pnpm commands reliably.
• Give client scope rows stable IDs so editing a new scope does not remount the input and drop focus.
• Add a Playwright regression that types into a scope field on the create-client flow.

Fixes #170.
Fixes #171.

Verification

• pnpm tidy
• pnpm build

Notes

• pnpm tidy still reports existing Biome schema/deprecation info and existing unrelated lint warnings.
• pnpm build still reports existing Vite large chunk warnings.