chore: sync schema with scrum4me@43a4294 + write metadata in log tools

PR #2 merged, so the StoryLog.metadata JSONB column is live. Sync
the vendored schema and wire `metadata` through to prisma.create in
log_implementation, log_test_result and log_commit. Cast via
Prisma.InputJsonValue because Zod parses the input as a generic
record while Prisma's JSON input type is invariant.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

prisma/schema.prisma

@@ -167,6 +167,7 @@ model StoryLog {
   status         TestStatus?
   commit_hash    String?
   commit_message String?
+  metadata       Json?
   created_at     DateTime    @default(now())
 
   @@index([story_id, created_at])