feat(docs): add Upshift Vaults section to FXRP overview

Author: fassko

docs/fxrp/overview.mdx

@@ -114,3 +114,12 @@ FXRP is deployed as an [Omnichain Fungible Token (OFT)](/fxrp/oft) using LayerZe
 ## Firelight
 
 <Firelight />
+
+## Upshift Vaults
+
+Upshift is part of the XRP finance stack on Flare Network.
+It inherits the transparency model of the [FAssets](/fassets/overview) system: minting and redemption are proof-backed, and vault interactions are recorded on-chain.
+
+- **Funds are on-chain:** User deposits, vault balances, withdrawal requests, and claims are executed as smart contract state changes on Flare.
+- **User ownership is verifiable:** A user's position is represented directly on-chain and can be queried from smart contracts.
+- **Instruction flow is auditable:** XRPL-triggered actions are executed on Flare via [Smart Accounts](/smart-accounts/overview) with [FDC](/fdc/overview) backed verification and onchain execution.