fix: propagate InjectParamsIntoContext error in StartInference and FinishInference

[unameisfine]

Same pattern as #968 (Validation handler) — applied to StartInference and FinishInference.

Problem

When InjectParamsIntoContext fails (e.g. corrupted params store), both handlers log a warning but continue executing with a broken context. Downstream calls to GetDeveloperAccessParams and GetTransferAgentAccessParams then fail silently, effectively bypassing access gates.

Fix

Return error immediately instead of continuing, matching the pattern from #968:

ctx, err := k.Keeper.InjectParamsIntoContext(sdk.UnwrapSDKContext(goCtx))
if err != nil {
    k.LogWarn("...", types.Inferences, "error", err)
    return nil, fmt.Errorf("cannot start/finish inference with stale params: %w", err)
}

Tests

TestStartInference_ReturnsError_WhenInjectParamsFails and TestFinishInference_ReturnsError_WhenInjectParamsFails — corrupt the params store with invalid protobuf, then call the handler:

• Without fix: FAIL — handler returns nil error, continues with broken params, access gates bypassed
• With fix: PASS — handler returns "cannot start/finish inference with stale params" immediately

[akup]

Same as #968

@unameisfine I think tests here is overkill and just add unneeded code. Please clear the tests from the PR

[unameisfine]

Done — removed both test files in 11d5d96. Only the two msg_server fixes remain.

[akup]

Done — removed both test files in 11d5d96. Only the two msg_server fixes remain.

And please rebase

[unameisfine]

Rebased on main (ec8f455).