feat(applications): overview page to manage pages and menu

[rubenvdlinde]

Rebuild of #40 (originally #26) on the page model of nextcloud#3100 / nextcloud#3099, see #13. Stacked on #52.

What changes

Inside Tables an application gets an overview to manage it: its name, address, settings, pages and menu.

• Route /application/{id}/overview, opened with "Overview" in the application's title row.
• Header: icon, name, description and the application's address, with a copy button and "Open application". The owner gets a menu to edit name, icon and members, import a scheme, transfer ownership or delete the application.
• Pages: a table of the application's pages, the start page first (its title, or "Dashboard"), with the type (Start page or Page with widgets) and what it shows (its widgets, and on the start page its tables and views). Managers get a "Design" link that opens the page in edit mode (?edit=1, new startInEditMode prop on GridPage), others "Open".
• Add page (owner): "Page with widgets" opens the page form of feat(pages): grid pages in the application UI (#3099, step 4) #49 (title, emoji, description, technical name), adds the page to the menu straight away and opens it in edit mode. "Table or view" and "Link" open the menu editor with a new entry of that kind.
• Menu (owner): a numbered preview (1, 1.1, 2, ...) with what each entry opens, and "Edit menu" to change it in place with the editor of the create dialog. The editor now offers the pages of the application as targets; only the dashboard item of a new application keeps its target. Saving replaces the menu through the context update and reloads the application.

Carried over from #40, and what changed because of nextcloud#3100 / nextcloud#3099

• Header, actions, menu preview and in-place editor, toEditableMenuItems, pageTitle, updateContextMenuItems: carried over. In the editor, feat(applications): overview page to manage pages and menu #40's isFixedItem became m4's opensNewStartPage.
• Grid pages in applications (frontend) nextcloud/tables#3099 keeps the start page at /application/{id} as it is, with the page bar under the description. feat(applications): overview page to manage pages and menu #40 replaced that route with the overview; here the overview has its own route and the start page stays. For the same reason the Tables navigation still collapses when an application opens (feat(applications): overview page to manage pages and menu #40 had changed that), and the existing context*.spec.ts need no change.
• Pages come from the context response (pages: title, emoji, page type, technical name); the overview loads each page from the page API for its widget count. feat(applications): overview page to manage pages and menu #40 counted page.content rows as widgets.
• "Page with widgets" uses r4's page form and POST .../pages with title, emoji, description and technical name.

Tests

Nextcloud 34 container (PostgreSQL 16), Playwright at 1600 x 1000, --timeout=120000:

• application.spec.ts: the 4 tests of feat(applications): standalone application shell with its own menu #52 plus: the overview lists the start page ("Dashboard", "Start page", "0 widgets") and a page added there gets a menu entry (intake_home) and opens in edit mode; menu entries reordered and nested with buttons keep their place after a reload; a menu entry pointed at a page of the application opens it. With context-menu.spec.ts: 9 passed (1.8m).
• context-grid-pages.spec.ts, context.spec.ts, context-navigation.spec.ts: 15 passed (7.6m).
• env -u ELECTRON_RUN_AS_NODE npx cypress run --component --spec cypress/component/menuItems.cy.js,cypress/component/gridLayout.cy.js,cypress/component/GridWidget.cy.js: All specs passed! 31 31 (adds toEditableMenuItems and pageTitle for context and page API pages).
• npm run lint: 0 errors, 1 inherited warning (src/store/store.js:176); npm run stylelint: clean; npm run build: OK.

Prepared in the Conduction fork for porting upstream by @remko48. Prepared with Claude Code.