Fix ty invalid assignment

[kadubhumika]

Description

Fixes the remaining ty invalid-assignment and related type-checking diagnostics across multiple files.

Changes made

• Fixed type annotations and optional Node handling in linked list implementations.
• Fixed type issues in the segment tree and binomial heap.
• Fixed typing for automatic differentiation and minimum cut implementations.
• Added explicit urllib.request import.
• Fixed the CPU scheduling selection type-checking issue.
• Added necessary assertions for image pixel access.

Validation

ty check --exclude-scripts

Result:

All checks passed!

[algorithms-keeper]

Closing this pull request as invalid

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