FLOW-8: Implement minimal YieldVault views

[liobrasil]

Closes: #139

Description

Implements minimal ViewResolver.Resolver views for FlowYieldVaults.YieldVault so the type no longer advertises view support while returning empty data.

• Adds YieldVaultInfo and YieldVaultBalance view structs.
• Implements YieldVault.getViews() and YieldVault.resolveView(_:) for both views.
• Fixes YieldVault.getStrategyType() to return the concrete (non-optional) type identifier.
• Adds scripts + regression coverage validating both views resolve for a live YieldVault.

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For contributor use:

• Targeted PR against master branch
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code follows the standards mentioned here.
• Updated relevant documentation
• Re-reviewed Files changed in the Github PR explorer
• Added appropriate labels

[m-Peter]

Suggested change

	/// Minimal view struct providing the YieldVault's current available balance for the vault's denomination. ///
	/// Minimal view struct providing the YieldVault's current available balance for the vault's denomination.

[m-Peter]

LGTM!