fix(ui): make the app fit the window it enforces a minimum for

The track list shared out its whole clientWidth across the resizable
columns while every row spends 24px on the favourite column and 2x8px
on its own padding before the first one starts, so the grid was always
exactly 40px wider than the box holding it and the last column was
clipped at every size (scrollWidth 1280 vs clientWidth 1240, measured).
Both numbers now live in one place and are read by the two call sites
that had written them out separately, which is how they came to
disagree.

The enforced minimum was 512x384, which the layout had never
supported: at 700x480 the eleven sidebar items needed 406px of a 352px
pane, overflow:hidden cut the last two off with nothing to scroll, and
Settings and Jobs could not be reached at all. The pane scrolls now,
the sidebar collapses to icons below 900px (its .collapsed mode existed
and only a manual drag ever reached it), the subtitle hides at the same
breakpoint so the title stops wrapping out of the 4em bar, and the
minimum is 800x600 - measured as where the shell still works rather
than picked as a round number.

backend/config/window.go

@@ -12,9 +12,17 @@ const (
 	// MinWidth is the smallest allowed window width in pixels.  Wails
 	// enforces this at runtime; it is also the floor below which a
 	// reported size is treated as bogus and not persisted.
-	MinWidth = 512
+	//
+	// 800x600 is where the shell was measured to still work, rather
+	// than a round number: below ~780 the header's subtitle wraps and
+	// pushes the title out of the 4em top bar, and below ~600 tall the
+	// eleven sidebar items no longer fit at once.  The previous
+	// 512x384 was aspirational — at 700x480 the sidebar overflowed
+	// behind the player bar with no scroll and Settings and Jobs could
+	// not be reached at all.
+	MinWidth = 800
 	// MinHeight is the smallest allowed window height in pixels.
-	MinHeight = 384
+	MinHeight = 600
 )
 
 // WindowConfig holds window size preferences.