Convert layer supports datetime / dict / list / url typed reads

[zeevdr]

Description

sdk/src/opendecree/_convert.py:60-86 supports str/int/float/bool/timedelta only. The proto TypedValue also has time_value, url_value, json_value, but Python callers receive raw strings and must parse manually.

Acceptance criteria

• Add datetime conversion via fromisoformat for time_value
• Add dict/list conversion via json.loads for json_value
• Add url-typed str alias for url_value
• Update typed getters and tests