feat(themes): Omarchy catalog, 12 light themes, Dark/Light Appearance picker

Expand the catalog from 11 themes (10 dark, 1 light) to 37 (24/13):
all 18 remaining Omarchy defaults (palettes from each theme's
colors.toml) plus 8 canonical light themes (Tokyo Night Day, Solarized
Light, One Light, Ayu Light, GitHub Light, Gruvbox Light, Everforest
Light, Kanagawa Lotus). Lupine leads the light list as the default
light theme; the app default stays tokyo-night.

Appearance panel: Dark/Light segmented filter (SSR-initialized from the
user's current theme), scrollable theme list, Bookshelf section pinned;
active row revealed on open. Light themes carry color-scheme: light and
the soft-shadow token set. Public-page theme selects get Dark/Light
optgroups. New moon/sun icons.

tailwind.config: safelist the new theme ids — Tailwind v3 purges custom
@layer base class selectors that appear in no scanned content file, so
an unsafelisted id silently ships without its CSS (found the hard way).

theme.ts: applyTheme now swaps only theme-* classes (changing theme
from the login select no longer wipes min-h-screen) and keeps the class
in sync on <html> for the new ThemeFlashGuard — a pre-paint inline
script on the four public pages that applies the saved theme before
first paint.

Kanagawa's UI accent uses crystalBlue (#7e9cd8) instead of Omarchy's
foreground-as-accent so links stay distinguishable from text.

templates/icons.templ

@@ -47,6 +47,11 @@ templ Icon(name string, extra string) {
 				<circle cx="15" cy="12" r="1"></circle>
 				<circle cx="9" cy="18" r="1"></circle>
 				<circle cx="15" cy="18" r="1"></circle>
+			case "moon":
+				<path d="M21 12.8A9 9 0 1 1 11.2 3a7 7 0 0 0 9.8 9.8z"></path>
+			case "sun":
+				<circle cx="12" cy="12" r="4"></circle>
+				<path d="M12 2v2M12 20v2M4.9 4.9l1.4 1.4M17.7 17.7l1.4 1.4M2 12h2M20 12h2M4.9 19.1l1.4-1.4M17.7 6.3l1.4-1.4"></path>
 			case "settings":
 				<circle cx="12" cy="12" r="3"></circle>
 				<path d="M12 2v3M12 19v3M2 12h3M19 12h3M5 5l2 2M17 17l2 2M19 5l-2 2M7 17l-2 2"></path>