feat: upgrade soroban-sdk to 26.1.0 for Protocol 27 compatibility

- Updates workspace soroban-sdk from 22.0.0 to 26.1.0
- Updates dev-dependencies to match
- All 21 tests passing
- WASM builds cleanly with stellar contract build --optimize

Closes #26

Author: MarcusDavidG

Cargo.toml

@@ -3,7 +3,7 @@ members = ["contracts/sharpy"]
 resolver = "2"
 
 [workspace.dependencies]
-soroban-sdk = { version = "22.0.0" }
+soroban-sdk = { version = "26.1.0" }
 
 [profile.release]
 opt-level = "z"

contracts/sharpy/Cargo.toml

@@ -10,7 +10,7 @@ crate-type = ["cdylib", "rlib"]
 soroban-sdk = { workspace = true }
 
 [dev-dependencies]
-soroban-sdk = { version = "22.0.0", features = ["testutils"] }
+soroban-sdk = { version = "26.1.0", features = ["testutils"] }
 
 [features]
 testutils = ["soroban-sdk/testutils"]