Integrate valgrind into existing test matrix

- Add valgrind installation step to test job
- Run all matrix tests under valgrind using CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_RUNNER
- Remove separate valgrind job in favor of integration with existing tests

Author: cursoragent

.github/workflows/ci.yml

@@ -60,6 +60,8 @@ jobs:
       - uses: actions/checkout@v4
       - name: Set up cargo cache
         uses: Swatinem/rust-cache@9d47c6ad4b02e050fd481d890b2ea34778fd09d6
+      - name: Install valgrind
+        run: sudo apt-get update && sudo apt-get install -y valgrind
       - name: Install PostgreSQL ODBC driver
         if: matrix.setup_odbc
         run: sudo apt-get install -y odbc-postgresql
@@ -74,6 +76,7 @@ jobs:
         env:
           DATABASE_URL: ${{ matrix.db_url }}
           RUST_BACKTRACE: 1
+          CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_RUNNER: "valgrind --error-exitcode=1 --leak-check=no"
 
   windows_test:
     runs-on: windows-latest