Fold thirty-one settings pages into fifteen categories with tabs

The sidebar was a flat scan of thirty-one rows; now it reads like a
settings app. Multi-subject categories (Input, Network & Sharing,
Applications, Users & Accounts, Privacy & Security, System) carry an
Appearance-style tab strip above the page, drawn by the shell so the
leaf pages themselves are untouched. The taxonomy lives in one new
file, services/SettingsRoutes.qml; the sidebar, the strip, route
validation, search breadcrumbs, and both generators derive from it.

ShellState.settingsPage still holds leaf ids, so every deep link, IPC
call, and search result keeps working — and now lands on the exact
tab. Dictation moves out of Sound onto its own page under Input, with
a handoff back to Sound for the microphone. The strip scrolls when
System's nine tabs outgrow a tiled window. All 161 contracts pass.

Claude-Session: https://claude.ai/code/session_01Ms2FbjQy31TVf3CEvQhGM8

config/dot/quickshell/manual/05-making-it-yours.md

@@ -2,10 +2,16 @@
 
 ## Settings
 
-`Super + I`. Thirty-odd pages covering displays, sound, network, appearance,
-power, printers, users, sharing, storage, updates and the rest. The search
-box at the top searches the settings themselves rather than just page names,
-so if you know what you want to change you can type it.
+`Super + I`. Fifteen categories down the side, covering appearance, displays,
+sound, input, network, power, accounts and the rest. A category with more than
+one subject in it opens a row of tabs above the page, which is where the
+narrower topics live: Printers is a tab of Network & Sharing, Dictation a tab
+of Input, and About, Software Update, Storage, Snapshots and this manual are
+tabs of System.
+
+The search box at the top searches the settings themselves rather than page
+names, and each result says where it will land, so if you know what you want
+to change you can type it and never touch the sidebar.
 
 ## Appearance