Fix Coverity issues from async auth feature

[nanangizz]

Summary

• Fix Coverity static analysis issues introduced by the async SIP client authentication feature (Asynchronous SIP client authentication #4816)
• Zero-initialize chal_param struct before use across 10 call sites to silence uninitialized user_data field warnings
• Add return value checks for pjsip_endpt_create() and pjsip_tsx_layer_init_module() in test helper
• Fix potential null pointer dereference in auth_async_test() cleanup path
• Check pjsip_rx_data_clone() return value in pjsua_call_on_incoming() and reject the call with 500 on failure (previously a failed clone would silently skip the on_incoming_call callback)
• Use std::move() for push_back in C++ test code

Coverity CIDs addressed

CID	Type	Fix
1645641, 1645645, 1645648, 1645649, 1645652, 1645655, 1645656, 1645658, 1645659	UNINIT	pj_bzero(&chal_param, sizeof(chal_param))
1645646, 1645653, 1645657	CHECKED_RETURN / FORWARD_NULL	Check return values in restore_endpt()
1645640	REVERSE_INULL	Use goto on_return instead of early return
1645647	CHECKED_RETURN	Check pjsip_rx_data_clone(), reject call on failure
1645651	COPY_INSTEAD_OF_MOVE	std::move(cred)

Not addressed (false positives)

CID	Type	Reason
1645642, 1645643, 1645644, 1645650, 1645654	WRAPPER_ESCAPE	unique_ptr<TestAccount> internal pointer escapes via acc->create() — intentional PJSUA2 account registration pattern in test code

Test plan

• Build passes with zero warnings (make -j3)

Co-Authored-By: Claude Code

[wosrediinanatour]

Isn't there a macro?

[nanangizz]

Good catch! Thanks for pointing it out.