Move UI to BoardUI with slate + salmon theme; add PDF plan export

- Adopt BoardUI (Pro init): theme tokens, Inter, .dark mode, Button,
  SegmentedControl, Meter, Skeleton and ThemeToggle; remap the app's
  color aliases onto BoardUI tokens and swap lucide for Remix icons
- Retint BoardUI's neutral ramp to cool slate with a salmon accent;
  drop the dotted background; raise muted text contrast
- Simplify the landing page and remove the overlap explorer
- Planner: explicit "I have this" toggle on grocery lines, pantry panel
  above the menu with the staples list spelled out, sticky aisle
  header fix, and a "Download PDF" plan export (jsPDF, lazy-loaded)
- Recipes: replace the family cabbage soup with Cade's Cabbage Soup
  (adds Bone-In Ham Steak to the catalog); remove Ham, Bean & Cabbage Soup
- Remove unused BoardUI components, dependencies and exports

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

utils/cx.ts

@@ -0,0 +1,61 @@
+import { extendTailwindMerge } from "tailwind-merge";
+
+/**
+ * Text-style classes from styles/typography.css.
+ *
+ * IMPORTANT: every text-* utility we define via @theme (e.g. `text-body-medium`,
+ * `text-title-1-semibold`) must be listed here. Otherwise tailwind-merge — which
+ * has no view of our Tailwind theme — treats them as text-color utilities and
+ * silently drops them when they appear in the same className as a real color
+ * (`text-foreground-full`, `text-text-primary`, etc).
+ *
+ * If you add or rename a text style in typography.css, mirror the change here.
+ */
+const TEXT_FAMILIES = [
+  "large-title",
+  "display-1",
+  "display-2",
+  "display-3",
+  "display-4",
+  "title-1",
+  "title-2",
+  "title-3",
+  "headline",
+  "body",
+  "body-2",
+  "caption-1",
+  "caption-2",
+] as const;
+
+const TEXT_WEIGHTS = ["regular", "medium", "semibold", "bold"] as const;
+
+const TEXT_STYLE_SUFFIXES = TEXT_FAMILIES.flatMap((family) =>
+  TEXT_WEIGHTS.map((weight) => `${family}-${weight}`),
+);
+
+const twMerge = extendTailwindMerge({
+  extend: {
+    classGroups: {
+      "font-size": [{ text: TEXT_STYLE_SUFFIXES }],
+    },
+  },
+});
+
+/**
+ * Merge Tailwind classes safely. Last-write-wins on conflicting utilities.
+ */
+export const cx = twMerge;
+
+/**
+ * Identity helper that gives the Tailwind IntelliSense extension a hook for
+ * sorting classes inside style objects (the extension doesn't sort inside
+ * plain object literals otherwise).
+ */
+export function sortCx<
+  T extends Record<
+    string,
+    string | number | Record<string, string | number | Record<string, string | number>>
+  >,
+>(classes: T): T {
+  return classes;
+}