chore(deps): batch dependency + CI-action bumps (supersedes Dependabot #43-#56)

[kutsenko]

Summary

Applies fourteen Dependabot bumps directly in one commit instead of
merging the PRs individually — they all touch pyproject.toml or
docker-publish.yml and would conflict-cascade. The individual
Dependabot PRs also fail build-and-push because Dependabot PRs get no
registry-secret access; this regular-branch PR does not have that
limitation.

pyproject.toml — >= version floors (no pinning):

Dependency	From	To	PR
setuptools (build-system)	>=69	>=82.0.1	#55
ocrmypdf	>=16.12.0	>=17.4.1	#47
pikepdf	>=9.0.0	>=10.5.1	#49
uvicorn	>=0.32	>=0.44.0	#54
img2pdf	>=0.5.0	>=0.6.3	#52
httpx	>=0.28	>=0.28.1	#48
ruff	>=0.9	>=0.15.10	#53
pytest-asyncio	>=0.23.0	>=1.3.0	#56
pytest-timeout	>=2.1.0	>=2.4.0	#51
pip-audit	>=2.7	>=2.10.0	#50

.github/workflows/docker-publish.yml — CI action majors:

Action	From	To	PR
docker/login-action	v3	v4	#43
docker/metadata-action	v5	v6	#44
docker/setup-buildx-action	v3	v4	#45
docker/build-push-action	v5	v7	#46

Closes #43, closes #44, closes #45, closes #46, closes #47, closes #48,
closes #49, closes #50, closes #51, closes #52, closes #53, closes #54,
closes #55, closes #56.

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