fix(docker): improve dockerignore list

[EmilyRagan]

What changed

Added depth matching to openc3/.dockerignore

Why it changed

• Python tests (at openc3/python/test) were being copied into the image because the ignore path only matched openc3/test/ -- this was adding ~200 unnecessary files to the published images
• for local builds, local python/.venv (and other paths) was being copied into the image and overwriting the image's uv-built .venv because the ignore path only matched openc3/.venv -- this is only an improvement/fix/change for locally built images, not published ones

Testing strategy

CI building images

Compared image sizes locally:

	main	branch	diff
Uncompressed, sum of layer sizes (docker history)	1,679,073,280 B	1,673,703,424 B	−5.37 MB (−0.32%)
Uncompressed, files under /openc3	366,994,945 B (10,264 files)	364,851,397 B (10,056 files)	−2.14 MB (−208 files)
Compressed (docker image inspect)	584,984,929 B	584,414,301 B	−0.57 MB (−0.10%)

Review notes

n/a

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.05%. Comparing base (0d8985e) to head (1ed775c).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3986      +/-   ##
==========================================
- Coverage   80.06%   80.05%   -0.02%     
==========================================
  Files         901      901              
  Lines       68370    68370              
  Branches     2699     2699              
==========================================
- Hits        54738    54731       -7     
- Misses      12976    12983       +7     
  Partials      656      656              

Flag	Coverage Δ
python	80.13% <ø> (+<0.01%)	⬆️
ruby-api	82.44% <ø> (-0.17%)	⬇️
ruby-backend	85.66% <ø> (ø)

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud