Install Rust rustfmt component in workflows

- Add 'rustup component add rustfmt' to both workflows
- Resolves 'cargo-fmt is not installed' error
- Now workflows can run formatting checks after successful compilation
- Combined with clippy, this completes the Rust toolchain setup
- Workflow should now complete successfully with all quality checks

.forgejo/workflows/build-artifacts.yml

@@ -63,6 +63,9 @@ jobs:
           
           # Install Rust clippy component
           rustup component add clippy
+          
+          # Install Rust rustfmt component
+          rustup component add rustfmt
 
       - name: Checkout repository manually
         run: |

.forgejo/workflows/simple-build.yml

@@ -26,6 +26,9 @@ jobs:
           # Install Rust clippy component
           rustup component add clippy
           
+          # Install Rust rustfmt component
+          rustup component add rustfmt
+          
           # Rust 1.89.0 is already installed in rust:1.89-slim-trixie
           # No need for rustup or toolchain management!
           echo "✅ Using pre-installed Rust from official image:"