Fix account deletion failing on non-archived notes

[thermcampos]

What to build

A user who confirms account deletion gets all of their data removed — notes regardless of archived state, note URLs, tags, and tasks — instead of the request failing and silently rolling back.

Today the account-deletion flow reuses the single-note delete path, which enforces the trash-can business rule "only archived notes may be deleted" and throws on the first non-archived note. Because the whole flow runs in one transaction, that exception aborts the entire account deletion. The archived-only rule is correct for the single-note API and must stay; account deletion needs its own bulk path that deletes every note the user owns, archived or not, along with their note URLs and any remaining tags, so the final user-row delete hits no foreign-key blockers.

Acceptance criteria

• A user with a mix of archived and non-archived notes (with tags and note URLs) can delete their account; all their rows are gone afterwards
• The single-note delete endpoint still rejects non-archived notes (trash-can rule unchanged)
• Tags owned by the user are fully removed during account deletion, not just orphaned ones
• Integration test against a real database covers the mixed archived/non-archived scenario end to end
• Existing account-deletion unit tests updated for the new flow

Blocked by

• None (can start immediately)