Skip sync for existing data and too-recent dates

- Check consumption table before fetching; return early if data exists
- Return "no data to fetch" for dates >= yesterday (not yet available)
- Add sync-month.sh script to sync all days in a month
- Add kill-server.sh script to free port 3000

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

kill-server.sh

@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+# Kill any process listening on port 3000.
+# Usage: ./kill-server.sh
+set -euo pipefail
+
+pids=$(lsof -ti:3000 2>/dev/null || true)
+
+if [ -z "$pids" ]; then
+  echo "No process on port 3000"
+else
+  echo "$pids" | xargs kill
+  echo "Killed: $pids"
+fi