Add fourmolu + hlint with scripts and git hooks (Atlas-style)

- Create scripts/build, scripts/test, scripts/run, scripts/install-hooks
- Create git-hooks/pre-commit (auto-format staged .hs files)
- Create git-hooks/pre-push (check formatting + hlint before push)
- Handle git worktrees correctly in hook installation
- Run fourmolu on all source files to fix existing formatting

scripts/build

@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+set -euo pipefail
+cd "$(dirname "${BASH_SOURCE[0]}")/.."
+
+echo "Formatting with fourmolu..."
+./hs fourmolu --mode inplace app/ src/ test/
+
+echo "Linting with hlint..."
+./hs hlint app/ src/ test/
+
+echo "Building..."
+./hs stack build --copy-bins --local-bin-path /work/build