feat: add validation for asset prices in total_assets calculation

[matias-gonz]

• Implemented checks for invalid prices (<= 0) in the calculate_total_assets function.
• Added error handling to raise ValueError with details of invalid prices.
• Introduced a new test to ensure that invalid prices trigger the appropriate exception.

[Copilot]

Pull Request Overview

Adds validation to reject invalid asset prices (≤ 0) in the total assets calculation, preventing incorrect computations from bad price data.

• Validates that all asset prices are positive before performing calculations
• Raises descriptive ValueError with details of which assets have invalid prices
• Adds test coverage for the new validation logic

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/tq_oracle/processors/total_assets.py	Adds validation loop to check for non-positive prices and raises ValueError with invalid price details
tests/processors/test_total_assets.py	Adds test case verifying ValueError is raised when prices are zero or negative

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[timbrinded]

merge when comment addressed