Replace fixed integration ports with ephemeral allocated ports

[teeschima]

Closes #656

Fantastic news: the tests now use ephemeral ports, and everything passes as expected.
Your code is now robust against shared/dev test port collisions.

🔧 What I changed
mod.rs
Added allocate_ephemeral_port():
Bind 127.0.0.1:0
Read local_addr().port()
Drop listener and return port
remote_run_tests.rs
Added mod network;
Replaced hardcoded 9245 with:
let port = network::allocate_ephemeral_port().expect("...");
server: --port using port.to_string()
client ping and run target use 127.0.0.1:{port}
parity_tests.rs
Replaced static ports 19_230, 19_231 with network::allocate_ephemeral_port() for both DAP tests.
🧪 Tests run
cargo test --workspace --all-features --tests -- --test-threads=8
cargo test --test remote_run_tests -- --test-threads=8
cargo test --test parity_tests -- --test-threads=8
All passed:

remote_run_tests: 1 passed
parity_tests: 17 passed
📌 Acceptance criteria status
Network tests reserve free ports dynamically: implemented
Pass selected port through test setup: done (port variable passed to server/client)
No fixed integration ports left: verified via grep
Parallel tests: no collision: pass confirmed in test environment

[drips-wave]

@teeschima Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

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