feat: start pages from templates and capture quick notes

[AmrMsCLL]

Stacked on #44.

What changes

• New pages can start from four built-in templates (meeting notes, journal, project brief, recipe), or from any page in the space marked "Use as a template". Template pages are listed separately on the space's pages view.
• New Quick note dashboard widget (capture): saves the text as a page or saves its first line as a task, in any space you can edit.
• The search palette gains a Create group: "New page" (in your personal space, then opens it) and "New task".
• POST /spaces/:id/notes accepts template, fromNoteId or text; the server builds the starting document and search text at creation. PATCH /notes/:id accepts template.

Migration

20261005060000_note_templates:

ALTER TABLE "notes" ADD COLUMN "template" BOOLEAN NOT NULL DEFAULT false;

Contract

• Dashboard widget types gain capture (server DTO and frontend registry in this PR).

Verification

• Frontend: test/notes.spec.tsx, test/dashboard.spec.tsx, test/search.spec.tsx (15 passed).
• Server integration: test/integration/notes.spec.ts, test/integration/dashboards.spec.ts (7 passed).
• Lint and build pass.