Adopt whynot-design tokens (WP-0017 Phase 1)

Replace vergabe's blue brand-* palette with whynot's near-black/paper/yellow
visual language. Tokens vendored at static/src/vendor/whynot-design/ (synced
from commit 9419f16 via scripts/sync-whynot-design.sh / make sync-whynot-design).

main.css imports the vendored CSS first, exposes ink/paper/hi as Tailwind
@theme tokens (bg-paper, text-ink, border-line, etc.), and re-tones every
component class (.btn-*, .card, .field-row, .phase-*, .form-input, .table-*,
.sidebar-*). Border radii drop to whynot's 0-4px; .card loses its shadow.

Legacy text-brand-* / bg-brand-* / border-brand-* template references are
kept working via @theme aliases that map the old blue scale onto the whynot
ink ramp — Phase 1 is tokens-only, no template churn.

btn-danger keeps an off-spec red (#B22222) as a local --danger var until
upstream defines a canonical destructive color.

base.html body class swapped: bg-slate-50 → bg-paper-2 text-ink.

Phase 2 (component adoption) deferred until whynot-design ships Lit web
components + missing atoms (Card, Modal, Input, Table, Toast). See
wiki/DesignSystem.md and history/2026-05-23-whynot-design-cross-framework-analysis.md.

Verified: 8/8 e2e tests pass; dev server boots; static/dist/main.css contains
no #3b5bdb references. Visual pixel-level verification still pending Bernd's
browser walk.

scripts/sync-whynot-design.sh

@@ -0,0 +1,39 @@
+#!/usr/bin/env bash
+# Synchronises the vendored copy of the whynot-design system from a pinned
+# upstream commit. Source: ~/whynot-design (worktree) or a clone from gitea.
+#
+# Usage: ./scripts/sync-whynot-design.sh [<commit-or-ref>]
+# Default: reads .whynot-design-ref from the vendor directory.
+#
+# See workplans/WP-0017-whynot-design-tokens.md for the adoption strategy.
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+VENDOR_DIR="$ROOT/static/src/vendor/whynot-design"
+REF_FILE="$VENDOR_DIR/.whynot-design-ref"
+SRC_REPO="${WHYNOT_DESIGN_SRC:-$HOME/whynot-design}"
+
+REF="${1:-}"
+if [[ -z "$REF" && -f "$REF_FILE" ]]; then
+  REF="$(cat "$REF_FILE")"
+fi
+if [[ -z "$REF" ]]; then
+  echo "Usage: $0 <commit-or-ref>   (or write a ref to $REF_FILE)" >&2
+  exit 2
+fi
+
+if [[ ! -d "$SRC_REPO/.git" ]]; then
+  echo "Source not found: $SRC_REPO" >&2
+  echo "Set WHYNOT_DESIGN_SRC or clone gitea:whynot/whynot-design there." >&2
+  exit 1
+fi
+
+mkdir -p "$VENDOR_DIR/tokens"
+git -C "$SRC_REPO" show "$REF:src/styles/colors_and_type.css" \
+    > "$VENDOR_DIR/colors_and_type.css"
+for f in colors.json type.json spacing.json index.json; do
+  git -C "$SRC_REPO" show "$REF:tokens/$f" > "$VENDOR_DIR/tokens/$f"
+done
+git -C "$SRC_REPO" rev-parse "$REF" > "$REF_FILE"
+
+echo "Vendor synced → $VENDOR_DIR (ref: $(cat "$REF_FILE"))"