Eiger pallet final

[illuzen]

Addressing some final issues:

REVERSIBLE-F-01 — set_high_security
No exit path has been added. recover_funds still does not clear HighSecurityAccounts or GuardianIndex. The team documented this permanence as intentional, so we understand that the risk is accepted.

Added documentation that recover_funds should be callable in perpetuity

REVERSIBLE-F-03 — orphaned holds
recover_funds now skips failed releases instead of aborting, which prevents new orphaned holds from being created. However, holds that were already detached from PendingTransfer metadata still have no repair path. No force-release extrinsic was added. One possible improvement would be to add a root-gated force_release_hold(account, asset, amount) extrinsic that can release holds directly.

This seems to only be possible due to migration, which we are skipping for testnet, as it would add code that wouldn't run on mainnet.

The following informational findings remain unaddressed: TREASURY-O-03, TREASURY-O-04, RUNTIME-O-01

Addressed the first two, the third was already addressed in a previous PR.

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Note

Low Risk
Low risk: changes are limited to additional event emission on already-handled mint failures and documentation/error cleanup, with no changes to successful reward or transfer execution paths.

Overview
Adds a new TreasuryMintFailed event in mining-rewards and emits it whenever minting to the treasury fails (both in the normal treasury payout path and when falling back from a miner mint failure), making lost-reward scenarios observable on-chain.

Cleans up reversible-transfers by removing the unused CallDecodingFailed error and expanding docs to explicitly state that high-security mode and recover_funds are intentionally permanent/repeatable. Expands the top-level documentation for the treasury pallet to better explain its configuration-focused role.

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