build: ⬆️ Bump Rust version to 1.90.0 (#362)

## Summary
- Bump Rust toolchain from 1.88.0 to 1.90.0 in
`operator/rust-toolchain.toml`
- Update hardcoded Rust version in
`.github/workflows/task-check-licenses.yml` to match

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: Ahmad Kaouk <56095276+ahmadkaouk@users.noreply.github.com>

.github/workflows/task-check-licenses.yml

@@ -14,7 +14,7 @@ jobs:
       - name: Install Rust toolchain
         uses: actions-rs/toolchain@v1
         with:
-          toolchain: 1.88.0
+          toolchain: 1.90.0
           override: true
       - name: Verify Licenses
         working-directory: operator

operator/rust-toolchain.toml

@@ -1,5 +1,5 @@
 [toolchain]
-channel = "1.88.0"
+channel = "1.90.0"
 components = [
     "cargo",
     "clippy",