Unify list rows, page headers and the sidebar

[enaboapps]

Closes #883. Stacked on #892, tracked in #891.

What changed

• Home status rows, Help setup and troubleshooting rows, paired devices, forwarding profiles and the setup guide's input-access row share one grouped-row card. Actions sit on the right and drop under the text only when the list is narrower than 560px, using a container query.
• Rows whose subject had a bare icon now use the same neutral icon tile as status rows, so text aligns across a list.
• Page headers put the subtitle under the title. The decorative Settings, Help and Paired devices corner icons are gone. Help, Switches and Mobile gain a one-line subtitle.
• Paired devices and Switch Forwarding were full nested views with their own h1 inside Mobile. They are now sections with an h2 header. The profile editor's focus fallback follows the new header class.
• The sidebar's active page is a raised surface with a brand bar and brand icon instead of a solid red block. It sets aria-current="page" and shows a Highlight outline under forced colours.

Validation

On this head:

• npm run lint passed
• npm test passed: 224 Vitest tests and 5 Node tests
• npm run build passed
• cargo fmt --check, cargo clippy --all-targets -D warnings and cargo test passed (566 tests, 1 ignored). No Rust changes in this stack.
• Rendered Home, Help, Mobile, profiles and setup in headless Chrome at 920px and 620px, light and dark.

Review follow-up

An independent review of this layer's head raised these points, now addressed:

• Under forced colours, the current page's nav button draws a CanvasText focus ring when focused. Before, its Highlight outline hid focus.
• Paired devices and Switch Forwarding are plain containers rather than labelled regions, so screen readers don't announce each tab's name twice. The empty paired-devices heading is now an h3.
• The profile editor's focus fallback is already covered by the existing test that deletes a custom profile and expects focus on New profile.

🤖 Generated with Claude Code

Rebase validation (2026-09-25)

Rebased onto current main (7fb8fce, including #881) in stack order. git range-diff shows every commit in this PR is patch-equivalent to its previous head, and the intended parent remains its PR base. On the final stack tip (40c75cc), Node 24.19.0 lint, tests and build passed; Rust 1.97.1 format check, Clippy and tests passed. An independent review of the updated PR heads found no actionable findings. CI is rerunning on each new head.