Make typography choosable instead of hardcoded

Theme.qml was the largest remaining thing in this desktop that could
only be changed by editing a file, and typeface is the first thing
someone changes when they want a desktop to feel like theirs. Interface
font, icon font, and the base text size are settings now.

The two font choices are deliberately separate lists. Theme.fontMono is
used only to draw glyphs -- workspace pills, the status cluster, search
icons -- so a plain monospace family there replaces every icon in the
shell with tofu. The picker offers only Nerd Fonts for that slot and
says why.

Candidates are rendered in the family they name. A list of font names
set in the current font tells you nothing about what you are choosing.

The four type sizes derive from the base rather than being stored
separately, so the relationship between body, caption, heading and title
survives a change instead of four numbers drifting apart.

hypr/looks.lua reads the same key. Following the preference only on the
QML side would leave the compositor and the shell disagreeing about the
interface font, which nobody notices until a tooltip renders in a
different typeface.

Only a family this machine reports is accepted: the value reaches
hl.config as a string, and a settings file moved between machines will
name fonts that are not installed. A missing family is reported rather
than silently substituted by fontconfig.

Also collapses the wallpaper grid to two rows. Sixty tiles is two
screens of pictures on a page that also holds typography, window
geometry and effects -- everything below it was unreachable without
scrolling past all of them.

Claude-Session: https://claude.ai/code/session_01BRvzt4H8XXLPVH5MyYdk9L

config/dot/quickshell/config/PreferenceSchema.qml

@@ -386,6 +386,36 @@ Singleton {
             detail: "A time earlier than the start simply means the next morning"
         },
 
+        // ── Typography ──────────────────────────────────────────────────────
+        // The single largest thing in this desktop that used to be changeable
+        // only by editing Theme.qml.
+        //
+        // interfaceFont is every piece of text a person reads. iconFont is used
+        // ONLY to draw glyphs -- workspace pills, the status cluster, search
+        // icons -- so it must carry Nerd Font glyphs; a plain monospace family
+        // there replaces every icon in the shell with tofu, which is why the
+        // picker offers them as a separate, filtered list.
+        {
+            key: "interfaceFont", type: "string", def: "Adwaita Sans", group: "typography",
+            // A family name, matched by fontconfig. Constrained because it also
+            // reaches hl.config as a string in hypr/looks.lua.
+            pattern: "^[A-Za-z0-9 ._-]{1,64}$",
+            label: "Interface font",
+            detail: "Used for every piece of text in the shell"
+        },
+        {
+            key: "iconFont", type: "string", def: "VictorMono Nerd Font", group: "typography",
+            pattern: "^[A-Za-z0-9 ._-]{1,64}$",
+            label: "Icon font",
+            detail: "Draws the shell's glyphs, so it must be a Nerd Font"
+        },
+        {
+            key: "interfaceFontSize", type: "int", def: 13, min: 10, max: 18, step: 1,
+            unit: "px", group: "typography",
+            label: "Interface text size",
+            detail: "The base size the rest of the shell's type scales from"
+        },
+
         // ── Accessibility ───────────────────────────────────────────────────
         // Backed by gsettings so GTK applications agree with the shell, and
         // pushed to the compositor as well where it has its own notion.