ci: run backend checks in one shell

.woodpecker.yml

@@ -7,8 +7,8 @@ steps:
     commands:
       - rustup component add rustfmt clippy
       - cargo install -j 2 sqlx-cli --version 0.8.6 --locked --no-default-features --features postgres,tls-rustls
-      - cd backend
       - |
+        cd backend
         ok=0
         i=1
         while [ "$i" -le 30 ]; do
@@ -24,10 +24,10 @@ steps:
           echo "sqlx migrate run failed after 30 attempts"
           exit 1
         fi
-      - cargo fmt --all -- --check
-      - cargo clippy -j 2 --all-targets --all-features -- -D warnings
-      - cargo test -j 2 --all
-      - cargo build -j 2 --release
+        cargo fmt --all -- --check
+        cargo clippy -j 2 --all-targets --all-features -- -D warnings
+        cargo test -j 2 --all
+        cargo build -j 2 --release
 
   frontend:
     image: node:20-bookworm