feat(db): Bun.SQL Kysely dialect for sqlite and postgres

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/db/src/json.ts

@@ -0,0 +1,14 @@
+/** Serialise a value for a JSON column (stored as text on both dialects). */
+export function toJson(v: unknown): string {
+  return JSON.stringify(v);
+}
+
+/** Parse a JSON column, returning `fallback` for null, undefined or invalid text. */
+export function fromJson<T>(s: string | null | undefined, fallback: T): T {
+  if (s == null) return fallback;
+  try {
+    return JSON.parse(s) as T;
+  } catch {
+    return fallback;
+  }
+}