fix(web): restore padding in provider sign-in setup box

[adampeterhiggins]

Summary

• Upstream fix(web): align provider settings with shared settings rows pingdotgg/t3code#10571 aligned provider settings with shared settings rows: ProviderSetupSection was converted to SettingsRows (which carry their own px-3 sm:px-4 py-3 padding), and the <div className="px-3 py-3 sm:px-4"> wrapper around ProviderInstanceCard's setup slot was removed.
• The fork's ProviderAuthSection still rendered free-form content that relied on that wrapper, so after the merge its content sat flush against the Setup box edges (see before shot).
• Converts ProviderAuthSection to the same SettingsRow structure as ProviderSetupSection: a sign-in row carrying the status line plus flow/sign-out controls, a sign-in method row holding the picker or pasted-credential form, and a readout row for the recorded method. The section now owns its own padding and matches the Antigravity setup rows in the same card.

Before / after

Signed in:

Signed out / disabled:

Test plan

• Verified in a real web client (vp run dev + seeded state): signed-in state shows padded rows with right-aligned Sign out; disabled state shows the enable block, status, and method picker rows
• vp run --filter web typecheck, vp lint, vp fmt --check on the touched file
• Verify the paste-credential form and waiting-flow (link expiry / callback input) visually on a provider that offers them

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