feat: allow skipping payments adjustments in the gh action

Description

The upload action computes a funding plan and, when more funds are needed, performs the top-up automatically (upload-action/src/filecoin.js:131-158). There is no way to tell the action to leave payment state alone.

Some users manage allowances and funding outside the action: their own deposit/allowance flow, a shared treasury, or a separate setup step. For them the action mutating payment state is unwanted and can fight their own management.

Proposed approach

Add an action input (e.g. skipPaymentSetup: true) that bypasses the funding-plan top-up and uploads with whatever allowances and balance already exist. When set:

• skip the calculateFilecoinPayFundingPlan / executeTopUp adjustment.
• still surface current account status so the run stays debuggable.
• fail clearly if existing funds/allowances are insufficient, rather than silently topping up.

Done criteria

• New input skips the action's payment adjustment when enabled; default keeps current behavior.
• Upload proceeds on existing allowances/balance with no deposit or allowance changes.
• Insufficient-funds case fails with an actionable message pointing at external setup.
• Documented in upload-action/action.yml and the action README.