Adds a fifth tab (◆ S3TT1NGS ◆) at the end of the dashboard tab
strip; moves the browser-notification controls out of the chrome
header into the new pane.
### Why
The chrome was carrying the notification controls as 'always-on
ergonomics' but the surface they belong on is operator preferences,
not navigation. With #589 / #701 likely adding more per-browser
preferences later (theme / density / etc.), having a dedicated
S3TT1NGS pane gives them a home so the chrome strip doesn't keep
accreting controls.
### Shape
- index.html: new `#tab-pane-settings` section with H2 + intro +
H3 'browser notifications' group; same notif-row DOM (same IDs)
migrated from the chrome
- flow.html: drops the duplicated notif-row from its chrome (FL0W
reused the dashboard's strip); adds a `◆ S3TT1NGS ◆ →`
cross-page link to `/#settings`. Notifications still fire on
FL0W when enabled — NOTIF.show() reads
Notification.permission + the hyperhive.notify.muted localStorage
key directly, no buttons needed in the page DOM.
- tabs.js: adds 'settings' to TABS array so hash routing activates
the pane
- dashboard.css: drops the chrome-anchoring `.tabbar #notif-row`
rule and the flow-page reuse comment, both obsolete; the general
`.notif-row` styling stays
- docs/web-ui.md: new `### S3TT1NGS tab` section; Chrome-header
bullet drops 'Notification controls' + adds S3TT1NGS; Browser
notifications section pointers at the new pane
### No JS or backend changes
Same IDs (notif-row, notif-enable, notif-mute, notif-unmute,
notif-status) so `NOTIF.bind()` in common.js wires the new pane
unchanged. NOTIF.show() dispatch is DOM-independent.
### Validation
`npm run --workspace @hive/dashboard build` clean (tabs.js 167.8kb,
flow.js 37.4kb, dashboard.css 50.2kb).
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