Refactor bot runtime and withdrawal selection

[phroi]

Why

• Finish the third iCKB Stack follow-up on top of Move app runtime flows onto SDK boundaries #33 by moving shared bot mechanics out of the app layer.
• Keep bot policy focused on balances, output slots, and thresholds while SDK owns ready-withdrawal selection.

Changes

• Reuse @ickb/node-utils for public client creation, signer lock ordering, loop sleep, JSON logging, and timeout handling.
• Remove bot-local logging/runtime helper copies and wire the bot to @ickb/node-utils.
• Delegate ready-withdrawal rebalance and cleanup selection to SDK selectors, preserving bot-specific policy at the app layer.
• Trim bot tests that duplicated SDK selector coverage while retaining bot policy and transaction behavior coverage.

[gemini-code-assist]

Code Review

This pull request refactors the bot application by migrating several utility functions and logic to shared packages. Specifically, it introduces the @ickb/node-utils dependency to handle logging, error management, and environment parsing, while delegating deposit selection and cleanup logic to the @ickb/sdk. Additionally, the PR replaces manual cell collection with the collectCompleteScan utility and removes redundant local implementations and tests. I have no feedback to provide.

[phroi]

LGTM

Phroi %187