Implement Storage Transactions in Demos Wallet Extension

[linear]

When a dApp interacts with a storage program, the wallet extension should open a confirmation modal for the user to review and approve the transaction.

Flow

1. dApp calls SDK storage method (e.g. StorageProgram.create(), setField(), write())
2. Wallet popup opens showing: operation type, storage address, data preview, fee
3. User approves → wallet signs and broadcasts
4. User rejects → dApp receives rejection

What exists

• SDK builds storageProgram transactions
• Node processes them (GCR handlers, RPC endpoints, fee calculation)
• Wallet already has signing flow for regular transfers

What's needed

• Wallet: recognize storageProgram tx type, render confirmation UI with operation details and fee
• SDK: route storage transactions through wallet provider (same pattern as transfers)

Acceptance criteria

• Storage operation triggers wallet confirmation popup
• User sees operation type, storage address, data preview, fee (1 DEM / 10KB)
• Approve → tx signed, broadcast, dApp gets hash
• Reject → dApp gets error
• Works for all operations: CREATE, WRITE, SET_FIELD, APPEND_ITEM, DELETE_FIELD