[Step 1] Core: Introduce HTTPX URL Builder Utility

[fderuiter]

Context

We need a centralized utility to dynamically sanitize and join paths without aggressive encoding.

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🗺️ Execution Plan

• Open src/imednet/utils/url.py.
• Create a new function build_safe_path(base_path: str, *segments: Any) -> str.
• Implement logic using httpx.URL("http://dummy").join(...) to normalize the joined path segments natively.

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✅ Definition of Done (Acceptance Criteria)

• build_safe_path function exists in src/imednet/utils/url.py.
• Function accepts a base path and any number of segment arguments.
• Function strips double slashes and outputs an unquoted, normalized relative path.