Fixed a bug where using Dict or Mapping type hints with Relationship()
would cause infinite recursion. The get_relationship_to() function now
properly handles dict/Mapping types by extracting the value type (second
type argument), similar to how it handles List types.

Changes:
- Added handling for dict and Mapping origins in get_relationship_to()
- Extracts the value type from Dict[K, V] or Mapping[K, V] annotations
- Added comprehensive tests for Dict relationships with attribute_mapped_collection

This resolves the RecursionError that occurred when defining relationships
like: children: Dict[str, Child] = Relationship(...)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

When using Annotated[type, Field(sa_column=...), Validator(...)], Pydantic V2
creates a new pydantic.fields.FieldInfo that doesn't preserve SQLModel-specific
attributes like sa_column and sa_type. This caused timezone-aware datetime
columns defined with DateTime(timezone=True) to lose their timezone setting.

The fix extracts the SQLModel FieldInfo from the original Annotated type's
metadata, preserving sa_column and sa_type attributes even when Pydantic V2
merges the field info.

Fixes timezone-aware datetime columns losing timezone=True when using
Annotated types with Pydantic validators.