fix: touch reachability, contrast and alignment

A pass over desktop, tablet and phone widths, measuring rather than
eyeballing.

The one that matters: a task could not be deleted on a phone. The delete
button is revealed on hover, touch devices report hover: none, so it sat
at zero opacity with nothing to reveal it. The README told people to hover
over a task and click it. It is now always visible where hover does not
exist.

Touch targets were under the 44px minimum: the checkbox at 24, delete at
32, the footer links at 23 tall. They now get 44px hit areas from overlays
that leave the drawn size alone, behind a pointer: coarse query so a mouse
keeps small precise targets and the full row stays draggable.

Two contrast failures in light mode. The date was the brand blue on the
near-white background at 3.54:1, so text now uses a darker --accent-text
and reads 5.14:1. Completed rows carried opacity 0.8 over an already
mid-contrast blue, which came to 3.34:1; the tint, the strikethrough and
the colour say "done" well enough without it, and dropping it gives 4.78:1.
Both themes now pass AA everywhere measured.

The checkbox sat vertically centred, so on a task wrapping to five lines
it floated in the middle of the block. Rows align to the top and task text
gets a 24px line box, matching the checkbox exactly, which also spaces
wrapped lines better.

Reduced motion was only honoured by the empty-state drawing. Svelte's
transitions run in JavaScript and never saw the media query, so tasks
still flew in on a stagger. The component reads the preference directly
and collapses its durations, and CSS covers the rest. The lift on a
dragged card stays, since it tracks the pointer rather than playing at you.

Long unbroken words already wrapped and no breakpoint scrolled sideways.

README.md

@@ -88,7 +88,7 @@ The date, storage, rollover, task and undo logic lives in `src/lib/` as plain mo
 ### Managing Tasks
 - **Add a task**: Type in the input field and press Enter
 - **Complete a task**: Click the checkbox next to the task
-- **Delete a task**: Hover over a task and click the delete icon, or press `Delete` with the task focused
+- **Delete a task**: Click the delete icon on the task (it shows on hover, and is always visible on touch), or press `Delete` with the task focused
 - **Undo a delete**: Press `Cmd/Ctrl+Z`. The task returns to where it was
 - **Reorder tasks**: Drag with a mouse, long-press then drag on touch, or focus a task and press `Alt+↑`/`Alt+↓`
 - **Clear input**: Press Escape while the input is focused