Import Application from panel.io.application, drop 3.9, and ruff

[ahuang11]

Application was dropped from panel.io.server which broke the Lumen imports
https://github.com/holoviz/panel/pull/7262/files#diff-aaf5dc2e57ff38e7660dbe2c7e08cd2b8a34242b382d40f049987b95f605e628L63

[ahuang11]

Discovered that Bokeh dropped 3.9 support, therefore Panel too, and so I also had to do drop it for Lumen holoviz/panel#6883

[codecov]

Codecov Report

Attention: Patch coverage is 46.87500% with 17 lines in your changes missing coverage. Please review.

Project coverage is 56.02%. Comparing base (6ff1468) to head (50e53ef).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
lumen/ai/translate.py	0.00%	7 Missing ⚠️
lumen/sources/base.py	33.33%	2 Missing ⚠️
lumen/transforms/base.py	33.33%	2 Missing ⚠️
lumen/ai/agents.py	0.00%	1 Missing ⚠️
lumen/ai/assistant.py	0.00%	1 Missing ⚠️
lumen/command/__init__.py	0.00%	1 Missing ⚠️
lumen/command/ai.py	0.00%	1 Missing ⚠️
lumen/ui/base.py	0.00%	1 Missing ⚠️
lumen/views/base.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #707      +/-   ##
==========================================
- Coverage   56.04%   56.02%   -0.03%     
==========================================
  Files          98       98              
  Lines       11829    11828       -1     
==========================================
- Hits         6630     6627       -3     
- Misses       5199     5201       +2     

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[github-actions]

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