feat(ui,infra): SvelteKit ui scaffold, Makefile, pre-commit, claude hooks

ui/: SvelteKit 2 + Svelte 5 + Tailwind 4 + shadcn-svelte (luma, lucide)
on bun with ultracite; adapter-static with SPA fallback; theme tokens
taken from msos. Dockerfile gains a bun stage that builds ui/build.
Makefile and pre-commit cover ruff, ty, ultracite and svelte-check;
.claude settings run the matching fixer after edits. docs/PRODUCT.md
captures product truth for the UI work.

Makefile

@@ -0,0 +1,31 @@
+.PHONY: sync check fix run ui ui-build db db-down
+
+sync:
+	uv sync --extra local
+	cd ui && bun install
+
+check:
+	uv run ruff format --check
+	uv run ruff check
+	uv run ty check
+	cd ui && bun lint && bun check
+
+fix:
+	uv run ruff format
+	uv run ruff check --fix
+	cd ui && bun fix
+
+run:
+	uv run python -m beaver_gateway
+
+ui:
+	cd ui && bun run dev
+
+ui-build:
+	cd ui && bun run build
+
+db:
+	docker compose --project-directory ../beaver-agent --profile db up -d postgres
+
+db-down:
+	docker compose --project-directory ../beaver-agent --profile db down