feat(calendar): replace event-edit drawer with anchored popover

[h4yfans]

Summary

• Clicking a calendar event now opens a compact popover anchored to the clicked chip instead of the full right-side drawer — title, location, start/end date+time, all-day toggle, notes, Save/Cancel. One component (CalendarEventPopover) handles both create and edit modes.
• Start/end rows reuse the same DatePickerContent widget already shipped in task due-dates, so there's one calendar + time picker in the app.
• Toolbar "+ New Event" now opens the same popover, anchored to the button rect.
• Delete calendar-event-editor-drawer.tsx (~160 LOC gone).

Why

The drawer felt disconnected from the chip the user just clicked — especially in day/week, where it shoves the grid aside. Screenshot reference in the task description shows the macOS-Calendar-style anchored popover we matched.

Architecture

• New types.ts extracts CalendarEventDraft and adds AnchorRect.
• New popover-position.ts extracts the anchor-rect positioning helper, shared with the existing marquee CalendarQuickCreateDialog.
• Chip onClick signature: (item) => void → (item, rect) => void. Thread through day / week / month / year views.
• Toolbar onCreateEvent captures its button's getBoundingClientRect() and passes up.
• Nested Radix Popover inside the outer Dialog uses an onPointerDownOutside / onInteractOutside escape hatch that checks [data-radix-popper-content-wrapper], so clicking into the date picker doesn't dismiss the outer popover.

Test plan

• pnpm typecheck:node ✓
• pnpm typecheck:web ✓
• pnpm --filter @memry/desktop lint — 0 errors
• pnpm --filter @memry/desktop test — all 4 calendar-page tests pass; all 16 quick-create tests pass
• calendar-page.test.tsx assertions updated from drawer (heading "New Event", Close button) to popover (role="dialog" with aria-label="Create calendar event", Cancel button)
• Manual smoke via pnpm dev — click event in day/week/month → popover appears next to chip; edit datetime via nested DatePickerContent; Save persists and refetches range; Escape / click-outside / Cancel dismiss; toolbar + New Event opens popover anchored to button; marquee "Add details" opens popover at the same anchor with prefilled title.