Restyle Bill profile and setup surfaces

[pattyboy813]

Summary

• restyle public Bill profiles and viewer-safe Payment Links/Socials details with compact Components V2 sections, thumbnails, separators, escaped metadata, and grouped HTTPS buttons
• add a durable, user-bound DM Start control and restyle every private profile wizard state without changing Worker/D1 contracts or dynamic-ID authorization
• restyle active, confirmation, and completed /bill setup surfaces with transient guild/member presentation data while preserving initiator checks and channel resolution
• document the private Start flow and add focused component-tree, restart, visibility, asset-fallback, row-limit, and secret-safety tests

Validation

• python3 -m compileall -q bill tests scripts
• python3 -m pytest -q — 88 passed
• changed-scope Ruff — passed (python3 -m ruff check bill tests/test_profiles.py tests/test_setup.py)
• cd worker && npm run check — typecheck passed; 228 tests passed

Notes

Full-repository Ruff still reports three pre-existing E501 violations in scripts/validate_release.py; this PR does not modify that file.

Stacked on #80 (patfaint-fix-bill-setup-channel) at 9828cc211f46027df4ff02ed1d6cc766f965f7f8. Do not merge independently of the lower layer.