build: use --profile=dev-release as the default cargo profile

[darioush]

Summary

Switch the nayduck worker's default (non---release) build to use the dev-release cargo profile instead of plain dev. The profile is defined in nearcore/Cargo.toml as release with lto=false, codegen-units=16, and debug-assertions=true — so we get release-style optimisations while keeping debug asserts on.

Motivation: expensive nightly tests run a long time. e.g. `tests::doomslug::ultra_slow_test_fuzzy_doomslug_liveness_and_safety` does heavy simulation in a 25ms-tick outer loop and is bottlenecked by codegen quality rather than I/O. The same logic applies to most other entries in nearcore's `nightly/expensive.txt`.

This is contained to nayduck's own build machines — pre-merge CI and local developer compiles are unaffected.

Changes

• `workers/builder.py`: pass `--profile=dev-release` to cargo when the test spec did not request `--release`; `build_type` returns `dev-release` so artefact copies pick the right `target/` subdir.
• `frontend/src/a_test.js`: the rendered cargo command on each test page now shows `--profile=dev-release` (or `--release`), matching what the worker actually runs.
• `frontend/src/Build.js`: build-page label changes from "Dev" to "Dev-release" to match.

`lib/testspec.py` and the DB schema are untouched — the test-spec grammar is unchanged.

Risk

Test runtime behavior may shift since `opt-level=3` enables aggressive inlining and the test profile changes from `dev`-inherited to `release`-inherited (overflow-checks on, panic=abort). Worth a manual nightly run before un-drafting to confirm no regressions in the expensive suite.

Test plan

• Run `python3 -c "import lib.testspec_test as m; m.test_testspec()"` — passed locally.
• Trigger a full nightly run against this branch and compare pass-rate + wall-time vs. current master.
• Spot-check a test page in the UI to confirm the rendered `cargo` command shows `--profile=dev-release`.