[Step 2] Core: Transport Layer Base URL Instantiation

[fderuiter]

Context

Transport clients must natively understand the base URL for relative path support, removing manual concatenation in requests.

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🗺️ Execution Plan

• Review BaseClient in src/imednet/core/base_client.py and Client in src/imednet/core/client.py (plus async equivalents).
• Ensure httpx.Client and httpx.AsyncClient are instantiated with base_url=self.base_url.

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✅ Definition of Done (Acceptance Criteria)

• httpx.Client explicitly includes the base_url argument.
• httpx.AsyncClient explicitly includes the base_url argument.
• Client .get() and .post() accept relative paths with no manual string prefixing.