[V136] Fix: Extend ZEC destination matching to Ragnarok and migrations

Background

Common outbound handling and voter action matching already normalize scheduled ZEC TEX and unified addresses before comparing them with observed receivers.

Ragnarok handling, migration dangling-action checks, and vault self-send checks still used direct address equality.

Changes

• Reuse the existing normalization through a shared destination comparison helper.
• Extend normalized matching to Ragnarok outbounds, migration dangling-action checks, and vault self-send checks.
• Preserve stored destination addresses and existing receiver-selection rules.
• Add a source guard against new direct destination comparisons, with explicit exceptions for existing valid uses.