migration(grantlee): add script to patch installed GrantleeConfig to use Qt6

app/patches/fix_installed_grantlee_config.sh

@@ -0,0 +1,33 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+GRANTLEE_INSTALL_DIR="${1:-./external/grantlee}"
+CONFIG_FILE="$GRANTLEE_INSTALL_DIR/lib/cmake/Grantlee5/Grantlee5Config.cmake"
+
+if [ ! -f "$CONFIG_FILE" ]; then
+  echo "Grantlee config not found at $CONFIG_FILE" >&2
+  exit 2
+fi
+
+# Replace Qt5 -> Qt6 in the installed Grantlee config to match Qt6 migration.
+# Be conservative: only replace find_package(Qt5 with find_package(Qt6
+# and occurrences of find_package(Qt5 REQUIRED X) -> find_package(Qt6 REQUIRED COMPONENTS X)
+
+cp "$CONFIG_FILE" "$CONFIG_FILE.bak"
+
+# handle common patterns
+sed -E -e 's/find_package\(Qt5Required Gui\)/find_package(Qt6 REQUIRED Gui)/g' \
+    -e 's/find_package\(Qt5 REQUIRED Gui\)/find_package(Qt6 REQUIRED COMPONENTS Gui)/g' \
+    -e 's/find_package\(Qt5 REQUIRED Core\)/find_package(Qt6 REQUIRED COMPONENTS Core)/g' \
+    -e 's/find_package\(Qt5 REQUIRED Qml\)/find_package(Qt6 REQUIRED COMPONENTS Qml)/g' \
+    -e 's/find_package\(Qt5 REQUIRED Qml\)/find_package(Qt6 REQUIRED COMPONENTS Qml)/g' \
+    -e 's/find_package\(Qt5 REQUIRED /find_package(Qt6 REQUIRED COMPONENTS /g' \
+    "$CONFIG_FILE.bak" > "$CONFIG_FILE"
+
+# quick sanity check
+if grep -q "find_package(Qt5" "$CONFIG_FILE"; then
+  echo "Warning: Some Qt5 references remain in $CONFIG_FILE" >&2
+  exit 3
+fi
+
+echo "Patched $CONFIG_FILE to use Qt6 (backup at $CONFIG_FILE.bak)"