feat(portal): add action buttons for application page elements

[BatLeDev]

Summary

• Adds a new actionButtons config block on the application page element (api/types/page-element-applications/schema.js) to display action buttons around an embedded application: fullscreen, capture, embed, datasets, with configurable style (icon / text / both), position (top / bottom) and alignment.
• New application-actions.vue component that renders the selected buttons. The datasets action fetches the application configuration to derive the list of datasets used and links either to the single dataset page or to /datasets?ids=… when multiple datasets are involved.
• Extends the datasets catalog page element to support filtering by an ids query param, so the multi-dataset link from the actions resolves to the expected catalog view.
• Refactors page-element-application.vue: action buttons can be rendered above or below the visualization; the preview screenshot path now reuses a single application fetch (via useLocalFetch outside preview) instead of re-fetching only in preview mode.
• Threads an optional actionStyle prop through application-capture.vue and application-embed.vue so the page element config can override the portal-level default.