fix: safe reserve capacity doubling with runtime monitor on insufficient stake

[martinconic]

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• I have read the coding guide.
• My change requires a documentation update, and I have done it.
• I have added tests to cover my changes.
• I have filled out the description and linked the related issues.

Description

1. On startup, if the node has insufficient stake for the configured ReserveCapacityDoubling, it now logs a warning and skips the on-chain UpdateHeight transaction. The node starts with the increased local capacity but without redistribution rewards.
2. Adds a background worker that checks the wallet balance every 10 minutes. If the stake is topped up to the required amount, it automatically triggers the UpdateHeight transaction to upgrade the node's status on-chain (noting that this triggers the standard freeze period ~ 2 rounds).

Open API Spec Version Changes (if applicable)

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