chore: remove insuficient asset ED and fee fallback to xyk pools

[enthusiastmartin]

Removes the paths that let non-whitelisted assets pay fees, and the insufficient-asset ED toll.

Changes

• Fee currencies limited to AcceptedCurrencies ‚ the XYK (X, DOT) tier is gone. set_currency, get_currency_price, account_currency, EVM permit gas and NativePriceOracle all apply the same whitelist check. XCM execution fees (Trader, XcmPaymentApi) are now limited to accepted currencies too.
• Insufficient-asset ED removed ‚ no charge or refund. AssetRegistry::register_external (call index 4) is deleted; external assets are onboarded through governance register only. SufficiencyCheck ‚ BannedAssetCheck; ban_asset is now the spam control. Legacy sufficients refs are kept on purpose (not released).
• DCA ‚when asset_in isn't an accepted currency, the fee is taken from the owner's free balance in their fee currency instead of swapping asset_in to DOT.
• Withdraw circuit breaker ‚ assets outside the whitelist are valued with the 10-minute EMA over their on-chain route instead of the XYK/DOT spot price. Fail-closed: an asset with no route cannot be withdrawn.

Migrations

• PurgeUnsupportedFeeCurrencies (multi-block) ‚ removes AccountCurrencyMap entries for non-accepted assets.
• RetireInsufficientEdPool (single-block) ‚ removes the treasury SUFFICIENCY_LOCK and ExistentialDepositCounter. Note that treasury keeps it, not refunds. currently around 100k

[claude]

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[github-actions]

Weight Diff Report

0 extrinsic(s) changed across 0 pallet(s). New: 0. Removed: 3.

Removed extrinsics (3)

Pallet	Extrinsic	RefTime	Proof	Reads	Writes
pallet_asset_registry	register_external	32.3M	4087	2	6
pallet_dca	on_initialize_with_buy_trade_with_insufficient_fee_asset	472.5M	31230	47	12
pallet_dca	on_initialize_with_sell_trade_with_insufficient_fee_asset	472.0M	31230	47	12

---

Threshold: ±10%. Base Weight::from_parts(ref_time, proof_size) compared; per-unit components ignored.

[github-actions]

Crate versions that have not been updated:

• runtime-integration-tests: v1.122.0
• pallet-evm-accounts: v1.7.0
• pallet-liquidation: v2.6.0
• pallet-otc: v2.5.0
• pallet-otc-settlements: v1.4.2
• pallet-xyk: v8.2.0
• hydradx-runtime: v449.0.0

Crate versions that have been updated:

• pallet-asset-registry: v3.5.0 -> v4.0.0
• pallet-dca: v1.21.1 -> v2.0.0
• pallet-transaction-multi-payment: v10.8.0 -> v11.0.0
• hydradx-adapters: v1.15.0 -> v2.0.0
• hydradx-traits: v4.14.0 -> v5.0.0

Crate versions that have been downgraded:

• pallet-dispatcher: v1.8.0 -> v1.7.4

Runtime version has not been increased.

[claude]

Claude Code Review

Claude Code Review is paused for this repository. To reconnect it, an admin of this repository's GitHub organization (or the account owner, for personal repositories) who can also manage your Claude organization's Code Review settings needs to re-link GitHub in Code Review settings. This is a one-time step.

_{Tip: disable this comment in your organization's Code Review settings.}

[cl0w5]

lgtm