[Feature] Apply Spring Advisors to that token usage metrics can be logged

### Description of Problem

Currently there is no way of getting metrics of your agent at a fluxnova level.

### Potential Solutions

Implement Spring 2.0.0 Advisors, which acts like AOP over spring calls. This can also be used to retrieve metadata including token usage. This can then be:
1. accessed via log monitoring tools
2. perhaps can be surfaced up to the control centre ui
3. can potentially be extendable so users can pass in their own advisors.

No files, tests, or entry points are identified in the issue. Start by locating the Spring call integration and reviewing the Spring 2.0.0 Advisor API, then define how token-usage metadata should be captured and logged; done should include a clear extension point for custom advisors and verified metric output.

Written by the indexing model from the issue text.