chore: improve cargo cache

[fresh-borzoni]

Summary

closes #479

Fix Rust CI caching:
hashFiles('**/Cargo.lock') was always empty because Cargo.lock is gitignored, so every build compiled from scratch.
removed from .gitignore

[fresh-borzoni]

@leekeiabstraction PTAL 🙏

[fresh-borzoni]

@leekeiabstraction changed, PTAL

[fresh-borzoni]

@leekeiabstraction fixed licenserc.yaml

[fresh-borzoni]

Looks good, twice as fast for rust now

[leekeiabstraction]

I ran a cargo audit to check for CVEs. Both of these traced back to testcontainers 0.25.2 as the common ancestor

  Crate:     astral-tokio-tar                                                                                                                                                       
  Version:   0.5.6                                                                                                                                                                  
  Title:     Insufficient validation of PAX extensions during extraction                                                                                                            
  Date:      2026-03-17                                                                                                                                                             
  ID:        RUSTSEC-2026-0066                                                                                                                                                      
  URL:       https://rustsec.org/advisories/RUSTSEC-2026-0066                                                                                                                       
  Severity:  1.7 (low)                                                                                                                                                              
  Solution:  Upgrade to >=0.6.0
  Dependency tree:                                                                                                                                                                  
  astral-tokio-tar 0.5.6
  └── testcontainers 0.25.2                                                                                                                                                         
      └── fluss-rs 0.2.0                                                                                                                                                            
          ├── fluss_python 0.2.0
          ├── fluss-examples 0.2.0                                                                                                                                                  
          └── fluss-cpp 0.2.0
                                                                                                                                                                                    
  Crate:     rustls-pemfile
  Version:   2.2.0                                                                                                                                                                  
  Warning:   unmaintained
  Title:     rustls-pemfile is unmaintained
  Date:      2025-11-28                                                                                                                                                             
  ID:        RUSTSEC-2025-0134
  URL:       https://rustsec.org/advisories/RUSTSEC-2025-0134                                                                                                                       
  Dependency tree:                                                                                                                                                                  
  rustls-pemfile 2.2.0
  └── bollard 0.19.4                                                                                                                                                                
      └── testcontainers 0.25.2                                                                                                                                                     
          └── fluss-rs 0.2.0
              ├── fluss_python 0.2.0                                                                                                                                                
              ├── fluss-examples 0.2.0
              └── fluss-cpp 0.2.0
                                                                                                                                                                                    
  error: 1 vulnerability found!
  warning: 1 allowed warning found                                                                                                                                                                                                                                                                                

[leekeiabstraction]

Raised issue for CVEs scanning: #480

[fresh-borzoni]

we need to fix this as well: #481

[leekeiabstraction]

Approved, TY for the PR