Add bitcoind/electrs setup to PostgreSQL CI

The PostgreSQL integration tests need BITCOIND_EXE and ELECTRS_EXE
environment variables to spawn regtest nodes, but the workflow was
missing the download, caching, and env var steps that rust.yml has.

Generated with the assistance of AI (Claude Code).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: benthecarman

.github/workflows/postgres-integration.yml

@@ -31,6 +31,29 @@ jobs:
       - name: Install Rust stable toolchain
         run: |
           curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --profile=minimal --default-toolchain stable
+      - name: Enable caching for bitcoind
+        id: cache-bitcoind
+        uses: actions/cache@v4
+        with:
+          path: bin/bitcoind-${{ runner.os }}-${{ runner.arch }}
+          key: bitcoind-${{ runner.os }}-${{ runner.arch }}
+      - name: Enable caching for electrs
+        id: cache-electrs
+        uses: actions/cache@v4
+        with:
+          path: bin/electrs-${{ runner.os }}-${{ runner.arch }}
+          key: electrs-${{ runner.os }}-${{ runner.arch }}
+      - name: Download bitcoind/electrs
+        if: "steps.cache-bitcoind.outputs.cache-hit != 'true' || steps.cache-electrs.outputs.cache-hit != 'true'"
+        run: |
+          source ./scripts/download_bitcoind_electrs.sh
+          mkdir bin
+          mv "$BITCOIND_EXE" bin/bitcoind-${{ runner.os }}-${{ runner.arch }}
+          mv "$ELECTRS_EXE" bin/electrs-${{ runner.os }}-${{ runner.arch }}
+      - name: Set bitcoind/electrs environment variables
+        run: |
+          echo "BITCOIND_EXE=$( pwd )/bin/bitcoind-${{ runner.os }}-${{ runner.arch }}" >> "$GITHUB_ENV"
+          echo "ELECTRS_EXE=$( pwd )/bin/electrs-${{ runner.os }}-${{ runner.arch }}" >> "$GITHUB_ENV"
       - name: Run PostgreSQL store tests
         env:
           TEST_POSTGRES_URL: "host=localhost user=postgres password=postgres"