Phase 5 sub-commit 1: DevConsole + child-output capture + Ctrl+` toggle

BackendConnection now captures the bundled FrankenPHP child's merged
stdout+stderr into a 500-line ring buffer, mirrors each line through
qCInfo(lcBundled) so terminal users still see logs, and exposes
childLogTail() / childLogLine for QML.

DevConsole.qml is an opt-in monospaced viewer with auto-scroll + clear
that the skeleton and the todo example bind to Ctrl+`. Dev mode (when
BRIDGE_URL is set, no bundled child) renders an explanatory hint.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

framework/qml/CMakeLists.txt

@@ -38,6 +38,7 @@ qt_add_qml_module(php_qml_bridge
     QML_FILES
         qml/RestClient.qml
         qml/AppShell.qml
+        qml/DevConsole.qml
 )
 
 target_include_directories(php_qml_bridge PUBLIC src/)