chore: add .githooks/pre-commit to auto-recompile paraglide on JSON changes

Committed hooks directory (.githooks/pre-commit) auto-runs `npm run paraglide`
and force-stages the generated JS output whenever ui/messages/*.json files are
staged, preventing svelte-check CI failures from stale paraglide output.

Added `just setup` recipe to configure core.hooksPath for new contributors.

.githooks/pre-commit

@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+# Auto-recompile paraglide messages when ui/messages/*.json files are staged.
+# Prevents svelte-check / CI failures caused by stale generated JS files.
+
+set -euo pipefail
+
+STAGED=$(git diff --cached --name-only)
+
+if echo "$STAGED" | grep -q '^ui/messages/'; then
+  echo "[pre-commit] ui/messages/*.json changed — recompiling paraglide..."
+  (cd ui && npm run paraglide --silent)
+  git add -f ui/src/lib/paraglide/messages/
+  echo "[pre-commit] paraglide output re-staged."
+fi

justfile

@@ -122,6 +122,13 @@ secrets-env:
 secrets-dashboard:
     doppler open dashboard
 
+# ── Developer setup ───────────────────────────────────────────────────────────
+
+# One-time dev setup: configure git to use committed hooks in .githooks/
+setup:
+    git config core.hooksPath .githooks
+    @echo "Git hooks configured (.githooks/pre-commit active)."
+
 # ── Gitea CI ──────────────────────────────────────────────────────────────────
 
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