Unify font sizes through qs.Commons.Style

Themes now drive typography the same way they drive colors: one [font]
base-size in shell.toml is the rem root, and every Style.font.<token>
(caption, bodySmall, body, subtitle, title, heading, display,
displayLarge, iconSmall, icon, iconLarge) derives from it via a fixed
multiplier. Themes can also pin individual tokens for stylistic
emphasis. base-size is clamped 11..13 until row-height tokens exist.

Bar dimensions move to the same singleton: [bar] size-horizontal /
size-vertical replace the hardcoded 26/28 in Bar.qml, exposed as
Style.bar.sizeHorizontal / sizeVertical.

Style.qml also resolves the fontconfig 'monospace' alias via fc-match
and exposes Style.font.resolvedFamily so panels can display the
concrete family. Watches ~/.config/fontconfig/fonts.conf so it tracks
'omarchy font set <name>'.

The qs.Ui kit (PillButton, Dropdown, Toggle, TextField, etc.) and
every first-party plugin (bar widgets, settings, menu, clipboard,
emoji, polkit, notifications, osd, image-picker, dev-gallery) now
bind to Style.font.* instead of pixel literals. Only three deliberate
display-scale outliers remain: the notification empty-state glyph and
the weather flyout's hero temperature pair, all commented.

Background plugin's applyTheme IPC fast-path also pushes shell.toml to
Style so theme swaps update typography and bar size without waiting
for inotify debounce.

Dev gallery (omarchy dev ui-preview) now ships a Typography section
that renders the full scale and theme tokens live, and its summon
command is fixed (omarchy-shell-ipc -> omarchy-shell).

shell/plugins/polkit/PolkitAgent.qml

@@ -269,7 +269,7 @@ Item {
           text: "\uf023"
           color: root.errorFlash ? Color.urgent : root.accent
           font.family: root.fontFamily
-          font.pixelSize: 20
+          font.pixelSize: Style.font.iconLarge
           width: 26
           height: root.fieldHeight
           horizontalAlignment: Text.AlignHCenter
@@ -289,7 +289,7 @@ Item {
             selectionColor: root.withAlpha(root.accent, 0.45)
             selectedTextColor: root.foreground
             font.family: root.fontFamily
-            font.pixelSize: 19
+            font.pixelSize: Style.font.iconLarge
             echoMode: root.responseVisible ? TextInput.Normal : TextInput.Password
             passwordCharacter: "\u2022"
             color: root.errorFlash ? Color.urgent : root.foreground
@@ -314,7 +314,7 @@ Item {
             color: root.errorFlash ? Color.urgent : root.foreground
             opacity: root.errorFlash ? 1 : 0.36
             font.family: root.fontFamily
-            font.pixelSize: 19
+            font.pixelSize: Style.font.iconLarge
             elide: Text.ElideRight
             visible: passwordInput.visible && passwordInput.text.length === 0
           }