fix: run emdash seed only on first launch via entrypoint.sh

- Remove emdash seed from Dockerfile build stage (no longer overwrites DB)
- Add entrypoint.sh that checks if data.db exists before seeding
- First launch: seed runs to populate DB
- Subsequent redeploys: DB exists, seed skipped, data preserved
- Also remove COPY data.db from runner stage (volume mount handles persistence)

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

entrypoint.sh

@@ -0,0 +1,10 @@
+#!/bin/sh
+# Only seed on first launch (when data.db doesn't exist)
+if [ ! -f data.db ]; then
+  echo "Database missing, running emdash init & seed..."
+  pnpm exec emdash init
+  pnpm exec emdash seed
+else
+  echo "Database exists, starting normally..."
+fi
+exec node ./dist/server/entry.mjs