v0.2.0 (10/N): bridge:export console command + QML hook

PLAN.md §12 *Data backup / export* called for "a bridge:export console
command and a UI hook for backup-to-file from v1". Shipping both now
so the v0.2.0 surface has the data-portability story end-to-end:

PHP side — `bin/console bridge:export <destination>`:
- Reads the source path from DATABASE_URL so it works in dev mode
  (developer's source-tree var/data.sqlite) and bundled mode (user
  data dir SQLite) without environment-aware logic.
- SQLite-only by design (PLAN.md §6 — single-instance SQLite-first);
  emits a clear error for non-sqlite:// URLs rather than pretending
  to support drivers that need driver-specific dump tooling.
- Overwrites the destination if it exists (the FileDialog or shell
  redirect that produced the path has already confirmed).
- 4 unit tests: happy path, non-SQLite URL, missing source,
  overwrite. Test count 24 → 28.

QML side — Q_INVOKABLE BackendConnection.exportDatabase(path):
- Bundled mode only; dev mode emits databaseExportFailed and
  returns false (developers own their SQLite directly).
- Accepts both filesystem paths and `file://` URLs (FileDialog
  results).
- Returns synchronously with bool but also emits async signals
  databaseExported(dst) / databaseExportFailed(reason) so QML
  can drive a snackbar / log without polling the return value.
- Removes any existing destination first (QFile::copy refuses
  to overwrite); the picker has already confirmed the choice.

Drive-by: parse_url() rejects sqlite:///abs/path on PHP 8.5+ (the
host-less triple-slash trips its strictness). Switched to a
prefix-strip — Doctrine DBAL only emits two URL shapes for
SQLite anyway (sqlite:///abs and sqlite://relative).

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

framework/qml/src/BackendConnection.cpp

@@ -472,6 +472,46 @@ QStringList BackendConnection::childLogTail() const
     return out;
 }
 
+bool BackendConnection::exportDatabase(const QString& destination)
+{
+    if (m_mode != Mode::Bundled) {
+        emit databaseExportFailed(QStringLiteral("dev mode: copy var/data.sqlite directly"));
+        return false;
+    }
+
+    const QString src = m_dataDir + QStringLiteral("/var/data.sqlite");
+    if (!QFileInfo::exists(src)) {
+        const QString msg = QStringLiteral("source not found: %1 (no data yet?)").arg(src);
+        emit databaseExportFailed(msg);
+        return false;
+    }
+
+    // QML's FileDialog returns `file://` URLs; unwrap to a local path.
+    QString dst = destination;
+    if (dst.startsWith(QStringLiteral("file://"))) {
+        dst = QUrl(destination).toLocalFile();
+    }
+    if (dst.isEmpty()) {
+        emit databaseExportFailed(QStringLiteral("destination path is empty"));
+        return false;
+    }
+
+    // QFile::copy refuses to overwrite. The FileDialog the user picked
+    // through has already confirmed any overwrite, so unlink first.
+    if (QFileInfo::exists(dst) && !QFile::remove(dst)) {
+        emit databaseExportFailed(QStringLiteral("could not remove existing destination: ") + dst);
+        return false;
+    }
+    if (!QFile::copy(src, dst)) {
+        emit databaseExportFailed(QStringLiteral("copy failed: ") + src + QStringLiteral(" → ") + dst);
+        return false;
+    }
+
+    qCInfo(lcBundled) << "exportDatabase:" << src << "→" << dst;
+    emit databaseExported(dst);
+    return true;
+}
+
 void BackendConnection::onChildFinished(int exitCode, QProcess::ExitStatus status)
 {
     Q_UNUSED(status);

framework/qml/src/BackendConnection.h

@@ -85,6 +85,15 @@ public:
     /// mode. Used by `DevConsole.qml` to seed its view on first show.
     Q_INVOKABLE QStringList childLogTail() const;
 
+    /// Bundled mode: copy `var/data.sqlite` to a user-chosen path
+    /// (typically a `Qt.labs.platform.FileDialog` result). Returns
+    /// true on success; on failure emits `databaseExportFailed` with
+    /// a human-readable reason. Use for an "Export my data" menu
+    /// item paired with the `bridge:export` console command for
+    /// CLI parity. Dev mode: returns false (developers own their
+    /// var/data.sqlite lifecycle directly).
+    Q_INVOKABLE bool exportDatabase(const QString& destination);
+
 signals:
     void urlChanged();
     void tokenChanged();
@@ -101,6 +110,9 @@ signals:
     void updateApplied();
     void updateApplyFailed(const QString& reason);
 
+    void databaseExported(const QString& destination);
+    void databaseExportFailed(const QString& reason);
+
     /// Emitted for each newline-terminated chunk read from the bundled
     /// FrankenPHP child's merged stdout+stderr stream. DevConsole.qml
     /// listens for these to populate its log view live.