feat(app): add a tasks page

[GuzmanPintos]

Tasks have a page now: Open tasks on the dashboard, or Tasks in the sidebar. It's a normal table, same as Deals. Filter by when something's due or who added it, switch between Open and Done, tick one off without leaving the row, click a row to open whatever it hangs off. You can also edit a task after saving it from the record's timeline, both the text and the due date, and a due date can be cleared now rather than only replaced.

Why: a task you add on a contact with no due date just vanishes. The dashboard only ever showed tasks already past due, and an undated one never is, so the only place it existed was that contact's timeline. Undated is the normal case, too. The date picker doesn't appear until you switch the composer over to Task, and nothing makes you use it. The dashboard card stays as it is. The page is where the rest of them live, undated included, under the No due date filter.

Creating a task still happens on a timeline rather than on this page, since it has to hang off a company, contact or deal.

Screenshots
Dashboard - "Open tasks" button following "Open deals" next to it

Tasks page

Edit a task

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Summary by cubic

Adds a paginated Tasks page with search, facets, sorting, and inline complete/edit; switches task due dates to calendar-day strings so due windows are consistent by viewer “today”. Previously, undated tasks were invisible outside timelines; the page now surfaces them and timeline tasks can be edited in place.

• Replaces activities.myTasks with activities.tasks returning { rows, total, facetCounts }, supporting q, pagination, sorting, and facets: status (open/done), due (overdue/today/week/later/none), and createdBy; requires today to compute windows.
• Adds activities.update to edit a task’s subject and dueAt with validation; dueAt is a calendar day (YYYY-MM-DD) or null, not an instant.
• Stores task due dates as UTC‑midnight days and serializes dueAt as YYYY-MM-DD. dashboard.summary now requires today and returns overdue task dueAt as a day string.
• UI: new /tasks route and rail item; table with tabs (Open/Done), facets (Due, Added by), search, sorting, pagination; inline complete; row click opens the linked record; timeline task editor with day picker; viewer‑day context and relative day labels; dashboard “Open tasks” button.

Required migration actions

• Replace any activities.myTasks calls with activities.tasks.
• Pass today (YYYY-MM-DD) to activities.tasks and dashboard.summary.
• When creating or updating tasks, send dueAt as a day string (YYYY-MM-DD) or null.
• Use activities.update to edit existing tasks.

^{Written for commit 47ba82a. Summary will update on new commits.}

[vercel]

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[cubic-dev-ai]

All reported issues were addressed across 35 files

<sub>Tip: instead of fixing issues one by one fix them all with cubic

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