CodeBench: 3 uutta promptisääntöä 5-kierroksen virheanalyysistä

1. Aikaleimakentät: server_default=func.now(), ei pakollisia Create-schemassa
2. Ei ylimääräisiä filter/search-endpointeja
3. Ei ylimääräisiä kenttiä spekin ulkopuolelta

kipina-codebench/prompts/code.md

@@ -31,6 +31,9 @@ RULES:
 - Python type unions: str | None (not Optional[str])
 - Tests: unique descriptive data per test, NOT generic "test_title" strings
 - Tests: PUT/update test data MUST include ALL required (non-nullable) fields, not just the field being updated
+- Timestamp fields (created_at, updated_at): ALWAYS use server_default=func.now() so they are NOT required in Create schema
+- Do NOT add filter/search endpoints — only standard CRUD (create, list, get, update, delete)
+- Do NOT add fields beyond what the spec defines — no extra created_at/updated_at unless in spec
 - Absolute imports only (from models import ..., from schemas import ...)
 - NO markdown fences inside file content — just raw code
 - Only test endpoints that exist in main.py — no extra tests