deploy.sh: detect JAVA_HOME and inject into systemd unit at deploy time

The pipekit system user has no PATH to java. deploy.sh now detects
JAVA_HOME by searching common locations and injects Environment= lines
into the installed unit file, making deploys portable across machines.

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

deploy.sh

@@ -182,8 +182,31 @@ step "Systemd unit"
 if [ ! -f "$UNIT_SRC" ]; then
     echo "  WARNING: $UNIT_SRC not found — skipping"
 else
+    # Detect JAVA_HOME — check PATH first, then search each location individually
+    JAVA_BIN="$(command -v java 2>/dev/null || true)"
+    if [ -z "$JAVA_BIN" ]; then
+        for _dir in /opt /usr/lib/jvm /usr/local/lib/jvm; do
+            [ -d "$_dir" ] || continue
+            JAVA_BIN="$(find "$_dir" -maxdepth 3 -name java -type f 2>/dev/null | head -1 || true)"
+            [ -n "$JAVA_BIN" ] && break
+        done
+    fi
+    if [ -z "$JAVA_BIN" ]; then
+        echo "  WARNING: java not found — JAVA_HOME will not be set in unit"
+        JAVA_HOME_DETECTED=""
+    else
+        JAVA_HOME_DETECTED="$(dirname "$(dirname "$(readlink -f "$JAVA_BIN")")")"
+        echo "  Detected JAVA_HOME: $JAVA_HOME_DETECTED"
+    fi
+
     echo "  Installing $UNIT_DST"
+    if [ -n "$JAVA_HOME_DETECTED" ]; then
+        # Inject Environment lines after WorkingDirectory= using printf to handle newlines portably
+        ENV_BLOCK="$(printf 'Environment=JAVA_HOME=%s\nEnvironment=PATH=%s/bin:/usr/local/bin:/usr/bin:/bin' "$JAVA_HOME_DETECTED" "$JAVA_HOME_DETECTED")"
+        awk -v env="$ENV_BLOCK" '/^WorkingDirectory=/{print; print env; next}1' "$UNIT_SRC" > "$UNIT_DST"
+    else
         cp "$UNIT_SRC" "$UNIT_DST"
+    fi
     echo "  Running systemctl daemon-reload"
     systemctl daemon-reload
     echo "  Enabling $SERVICE_NAME service"