Context

Part of #2679 (umbrella PersistentDialog migrations). Reference implementation: PR #2742 (migrated ProfileImportExportDialog).

What to do

Migrate `src/gui/PropDashboardDialog.{cpp,h}` from `QDialog` to inherit from `PersistentDialog`, following the exact recipe used in PR #2742.

File sizes (for context):

• `PropDashboardDialog.cpp` — 1164 lines
• `PropDashboardDialog.h` — 82 lines

Why this one first: smallest of the three remaining dialogs and has no inline-construction complications.

Recipe (copy from PR #2742)

1. Header — replace `: public QDialog` with `: public PersistentDialog`, drop `m_titleBar`/`m_bodyLayout` members and the `setFramelessMode` declaration.
2. Constructor — change initializer list to `: PersistentDialog("Propagation Dashboard", "PropDashboardDialogGeometry", parent)`, drop the manual frameless-chrome setup, build dialog content into `bodyWidget()` instead of a hand-rolled body widget.
3. Drop the standalone `setFramelessMode` method — base class provides it.
4. `closeEvent` — forward to `PersistentDialog::closeEvent` instead of `QDialog::closeEvent`.
5. `MainWindow.cpp` — change the lazy-construct block at line 5517-5527 to a single `showOrRaisePersistent(m_propDashboardDialog, m_propForecast)` call.
6. `MainWindow.cpp` — remove the `qobject_cast` branch at line 11628 from `setFramelessWindow()` — base class auto-propagates via `m_persistentDialogs` registry.
7. `MainWindow.h` — change `QPointer m_propDashboardDialog;` at line 495 to `QPointer m_propDashboardDialog;`.

AppSettings geometry key

Use `PropDashboardDialogGeometry` (PascalCase, matches existing convention).

Acceptance criteria

• `PropDashboardDialog` inherits from `PersistentDialog`.
• `m_propDashboardDialog` is typed `QPointer` (no `QDialog` fallback).
• Lazy-construct site uses `showOrRaisePersistent`.
• `setFramelessWindow()` no longer has an explicit `qobject_cast` branch.
• Geometry persists across launches under AppSettings key `PropDashboardDialogGeometry`.
• No behavior change in the propagation dashboard's content (panels, charts, refresh logic).

Pickup

Mechanical migration matching PR #2742's recipe. AetherClaude-eligible.

73, Jeremy KK7GWY & Claude (AI dev partner)