- Fix missing `import importlib.util` that caused NameError on Python 3.12+
  (root cause of PR #374 failures)
- Replace deprecated `find_module`/`load_module` with `find_spec`/`module_from_spec`
  in plugin loader and doc generator
- Remove Python <3.8 `pkg_resources` fallback (dead code since 3.8 dropped)
- Update CI matrix: test Python 3.10/3.11/3.12/3.13/3.14
- Fix CI test step: use `--without plugins,lint` to avoid installing
  incompatible old plugin test deps on newer Python versions
  (plugin tests run in Docker, host only needs pytest + testcontainers)
- Mark plugins and lint dependency groups as optional
- Change plugin dep pins from exact versions to `>=` ranges so
  poetry lock resolves on newer Python (actual test versions unchanged,
  controlled by support_matrix in each plugin + Docker)
- Update deps: unpin psutil, loosen wrapt/uvloop/grpcio-tools constraints
- Remove uwsgi from dev deps (doesn't build on 3.12+, tested via e2e)
- Update testcontainers DockerCompose usage for v4 API compatibility
- Replace unapproved getsentry/paths-filter with dorny/paths-filter
- Update docker/Makefile and Container.md for 3.10-3.14

Verified: Docker images build and agent loads all 35 plugins successfully
on Python 3.10, 3.11, 3.12, 3.13, and 3.14.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>