Attach app-server middleware stack to /api/v1 routes

[694410194]

Summary

• attach the existing app-server rate-limit, timeout, security-header, and content-type middleware to the /api/v1 router
• keep the current trace and permissive CORS layers intact while activating the protections already implemented in middleware.rs
• leave handler logic unchanged and scope the fix to router construction only

Verification

• git diff --check
• static review of src/cortex-app-server/src/lib.rs against the middleware definitions in src/cortex-app-server/src/middleware.rs
• Rust toolchain was not available in this environment, so cargo test / cargo check could not be run here

[greptile-apps]

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