feat: add JSON-compatible repr and to_dict for query result types

[atharva-deopujari]

Summary

Adds to_dict() and __str__() methods to query result dataclasses so that print(result) produces human-readable JSON output instead of the default dataclass repr.

Currently, printing a query result gives an unreadable blob of nested dataclass reprs. After this change:

result = collection.query.fetch_objects(limit=2)
print(result)
# Pretty-printed JSON with proper indentation

Classes Updated

• MetadataReturn, GroupByMetadataReturn
• Object, ObjectSingleReturn (via _Object)
• GroupByObject
• GenerativeSingle, GenerativeGrouped
• GenerativeObject, GenerativeReturn
• Group, GenerativeGroup
• GroupByReturn, GenerativeGroupByReturn
• QueryReturn
• _CrossReference

Design Decisions

• Vectors longer than 8 elements are truncated in string output to keep display manageable (e.g., [0.1, 0.2, ..., "... (1536 total)"])
• Special types (UUID, datetime) are converted to strings
• Nested objects with to_dict() are serialized recursively
• Only non-None metadata fields are included to reduce noise
• to_dict() returns raw dicts for programmatic use; __str__() wraps it in json.dumps with indentation

Fixes #881

[orca-security-eu]

Orca Security Scan Summary

Status	Check	Issues by priority
Passed	Infrastructure as Code	0   0   0   0	View in Orca
Passed	SAST	0   0   0   0	View in Orca
Passed	Secrets	0   0   0   0	View in Orca
Passed	Vulnerabilities	0   0   0   0	View in Orca

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[atharva-deopujari]

I agree with the CLA.