Handle responseData as both string and dict

[piekstra]

[#65]

Summary

• Fix TypeError when devices return responseData as a dict instead of a JSON string
• Add unit tests for pass_through_request covering both cases

Problem

Some devices (e.g., Archer A8 routers) return responseData as an already-parsed dict rather than a JSON string. The code was unconditionally calling json.loads() which fails with:

TypeError: the JSON object must be str, bytes or bytearray, not dict

Solution

Check the type of responseData before attempting to parse it:

• If it's a string, parse it with json.loads()
• If it's already a dict, return it directly

Test plan

• Added unit tests covering both string and dict responseData cases
• Added test for failed requests returning None
• All new tests pass locally

Note

This may not fully resolve Archer router support since the device commands may differ from smart plugs. However, this fix removes the immediate crash and allows further investigation.

CI Note

This PR should be rebased after #80 is merged to get CI passing.