Strengthen Playwright auth path handling

[mikeldking]

Summary

• centralize the Playwright auth constants in app/tests/constants.ts and expose uppercase snake case paths so all scripts reuse the same values
• make the Playwright config aware of its true directory, resolve the tests dir and storage state from that location, and run the dev server command via pnpm --dir so tests can execute from anywhere
• update auth.setup.ts, member-access.spec.ts, and viewer-access.spec.ts to import the shared constants instead of hard-coding paths

Testing

• Not run (not requested)

[cursor]

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