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/install-hooks

@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+# Install git hooks for the roux-server project.
+# Run once:  ./scripts/install-hooks
+set -euo pipefail
+
+HOOK_SRC="$(cd "$(dirname "${BASH_SOURCE[0]}")/git-hooks" && pwd)"
+# Determine git hooks directory — supports both regular repos and worktrees
+GIT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)/.git"
+if [ -f "$GIT_DIR" ]; then
+    # Worktree: .git is a file pointing to the real gitdir
+    GIT_DIR="$(cut -d' ' -f2 "$GIT_DIR")"
+fi
+HOOK_DST="${GIT_DIR}/hooks"
+
+mkdir -p "$HOOK_DST"
+echo "Installing git hooks from $HOOK_SRC -> $HOOK_DST"
+
+for hook in "$HOOK_SRC"/*; do
+    name=$(basename "$hook")
+    ln -sf "$hook" "$HOOK_DST/$name"
+    echo "  $name installed"
+done
+
+echo "Done."