Consolidate message boxes into one non-modal, copiable, standard-button ORE Studio dialog

Introduce a single ORE Studio-specific message box widget that every call site uses instead of ad-hoc QMessageBox calls or the existing MessageBoxHelper. Consumers should only ever state the text and which buttons they want; everything else — button styling (standard ORE buttons, not raw Qt defaults), selectable/copiable message text (so the text can be pasted into an LLM chat or a bug report verbatim), and, critically, non-modal presentation so the QA Validation Runner's screenshot-capture steps can still interact with other windows while the message box is open — is common code owned by the widget itself. MessageBoxHelper already exists as a partial consolidation point (MessageBoxHelper.cpp) but 14 files still construct QMessageBox directly, bypassing it entirely (e.g. CatalogDetailDialog.cpp, AddItemDialog.cpp, MasterPasswordDialog.cpp, TenantOnboardingWizard.cpp, PublishBundleWizard.cpp, ScriptEditorMdiWindow.cpp — see References for the full list found by grep), and even the 250+ files that do go through MessageBoxHelper inherit whatever modal/button/copiability behaviour that helper currently has, which is not yet what's wanted. This capture is for building the new widget (or upgrading MessageBoxHelper in place) and then migrating every call site to it.

Message boxes today are inconsistent in three concrete ways discovered doing manual QA and screenshot capture this sprint: buttons don't use ORE Studio's standard button styling; the boxes are modal, which blocks the QA Validation Runner's test-scenario screenshot steps from clicking on or focusing a different window while a message box is up, making some scenario steps impossible to automate/capture as written; and message text isn't selectable, so a tester or developer can't copy an error/warning verbatim to paste into an LLM chat for triage. Consolidating on one widget, where consumers only supply text and button choice, fixes all three at once and prevents the same inconsistency from being reintroduced at new call sites.

• MessageBoxHelper.hpp / MessageBoxHelper.cpp — existing partial consolidation point; candidate to extend in place.
• Files still constructing QMessageBox directly, bypassing MessageBoxHelper (grep QMessageBox:: without MessageBoxHelper in the same file, 14 hits at time of writing): refdata/src/CatalogDetailDialog.cpp, application/src/AddItemDialog.cpp, synthetic/src/MarketSimulatorWindow.cpp, synthetic/src/FxSpotRateEditor.cpp, application/src/MasterPasswordDialog.cpp, application/src/TagSelectorWidget.cpp, synthetic/src/FeedDialog.cpp, compute/src/ReportDefinitionController.cpp, admin/src/TenantOnboardingWizard.cpp, compute/src/ServiceDashboardMdiWindow.cpp, refdata/src/CatalogMdiWindow.cpp, refdata/src/PublishBundleWizard.cpp, application/src/ScriptEditorMdiWindow.cpp, application/src/ScriptLibraryPanel.cpp (all paths relative to projects/ores.qt/).
• Capture screenshots for the Currency Pairs manual chapter — the scenario that surfaced the modal-blocking problem while designing the "Inverted Pair" rejection dialog capture step.

• QA Validation Runner: in-app test tracking for the multi-worktree fleet