ci: bump action pins to current (#46)

- actions/checkout@v3 -> @v6
- astral-sh/setup-uv@v3 -> @v8.2.0

Leaves codecov-action@v4.0.1 untouched (separate decision).

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: lesnik512

.github/workflows/main.yml

@@ -16,8 +16,8 @@ jobs:
   lint:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
-      - uses: astral-sh/setup-uv@v3
+      - uses: actions/checkout@v6
+      - uses: astral-sh/setup-uv@v8.2.0
       - run: uv python install 3.14
       - run: |
           uv sync --all-extras --all-groups --frozen --no-install-project
@@ -43,8 +43,8 @@ jobs:
           --health-timeout 5s
           --health-retries 5
     steps:
-      - uses: actions/checkout@v3
-      - uses: astral-sh/setup-uv@v3
+      - uses: actions/checkout@v6
+      - uses: astral-sh/setup-uv@v8.2.0
       - run: uv python install 3.14
       - run: |
           uv sync --all-extras --all-groups --frozen --no-install-project