Conflux's Logo Have Bad Display in Dark Mode

### What is this about?

Currently, Conflux's logo can be displayed in MetaMask, but its display is not good in dark mode. For example, when network is requested to change in dark mode, the logo will be totally black:

It would be better if a new logo is replaced, and I'm willing to provide the solution

### Scenario

- GIVEN user in dark mode
- WHEN the user is requested to change to conflux network
- a totally black logo will appear

### Design

_No response_

### Technical Details

_No response_

### Threat Modeling Framework

_No response_

### Acceptance Criteria

_No response_

### Stakeholder review needed before the work gets merged

- [ ] Engineering (needed in most cases)
- [ ] Design
- [ ] Product
- [ ] QA (automation tests are required to pass before merging PRs but not all changes are covered by automation tests - please review if QA is needed beyond automation tests)
- [ ] Security
- [ ] Legal
- [ ] Marketing
- [ ] Management (please specify)
- [ ] Other (please specify)

### References

_No response_

Start by locating the Conflux logo asset and the network-change request UI in the MetaMask extension, then reproduce the reported scenario in dark mode. Done means the Conflux logo is clearly visible when the user is asked to switch networks, with the behavior verified in the relevant UI.

Written by the indexing model from the issue text.