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.

.claude/rules/stack-and-commands.md

@@ -1,19 +1,32 @@
 ## Stack
 
-<!-- TODO: Fill in language, frameworks, and key dependencies -->
-- **Language:**
-- **Key deps:**
+- **Language:** Python 3.12 (Django 6), Node 22 (Vite + Tailwind v4)
+- **Key deps:** Django, htmx, Alpine.js, Tailwind v4, whynot-design (vendored
+  under `static/src/vendor/whynot-design/`)
 
 ## Dev Commands
 
 ```bash
-# TODO: Fill in the standard commands for this repo
-
 # Install dependencies
+uv sync                     # Python
+npm ci                      # Node (Vite/Tailwind)
 
-# Run tests
+# Run dev stack
+make db                     # Start postgres if not running
+make dev                    # Django runserver on :9000
+make css                    # Tailwind/Vite watcher (rebuilds main.css)
 
-# Lint / type check
+# Build CSS bundle for prod / for verification
+npm run build               # → static/dist/main.css
 
-# Build / package (if applicable)
+# Re-vendor the whynot-design system from a pinned upstream commit
+make sync-whynot-design     # reads .whynot-design-ref by default
+                            # or: ./scripts/sync-whynot-design.sh <ref>
+
+# Tests / lint
+make test                   # uv run pytest
+make lint                   # ruff + mypy
 ```
+
+See `wiki/DesignSystem.md` for the whynot-design adoption status (Phase 1
+tokens+CSS done; Phase 2 components deferred) and local style conventions.