…2605)

Collapses the lazy-construct + non-modal + geometry-persist + frameless-
chrome boilerplate shared by every persistent dialog in MainWindow into a
single base class.  Subclasses fill in their content via bodyWidget() and
the base owns:

  * The outer (titleBar + bodyWidget) layout and frameless title-bar widget.
  * FramelessResizer installation (8-axis resize on the top-level window).
  * setFramelessMode(bool) — flips Qt::FramelessWindowHint while preserving
    geometry and toggles the custom title bar / body margins.
  * Geometry persistence under an AppSettings key.  Save fires on close
    (canonical, disk-flushed) AND on move/resize (in-memory, crash-resilient
    — matches ProfileManagerDialog's existing contract).  Restore deferred
    to first showEvent() so subclasses can call setMinimumSize() in their
    ctor without the just-restored geometry being clipped.

MainWindow gains a showOrRaisePersistent<T>(slot, ctorArgs...) template
that collapses the ~10-line menu-callback boilerplate to one line and
auto-registers each dialog in m_persistentDialogs.  setFramelessWindow()
walks that list instead of carrying an explicit qobject_cast branch per
dialog — new persistent dialogs propagate automatically.

Migrates ProfileManagerDialog as the pilot per the issue's migration plan:
-95 LOC of removed boilerplate, the explicit setFramelessWindow() branch
gone, behavior preserved (the same "ProfileManagerDialogGeometry" key
keeps prior sessions' saved geometry intact).

Principle V.

The header refactor in 137da71 introduced an inline forward declaration
"class QTabWidget* m_tabs;" inside namespace AetherSDR — which declares
AetherSDR::QTabWidget (a new incomplete type) rather than referencing
the global ::QTabWidget.  The .cpp then used operations on the
incomplete type, breaking the build on every platform.

Move the forward declaration outside the namespace alongside the other
Qt class forward-decls (QLineEdit, QListWidget, QPushButton, QCheckBox).

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