chore: valid packaging metadata, flake8 config file, ignore local config with secrets

pyproject.toml carried requirements.txt comment lines as dependencies, which
fails PEP 508 parsing. flake8 never read [tool.flake8] from pyproject, so the
settings move to .flake8 and pre-commit runs the full rule set. config.json
(holds the CivitAI API key and machine paths) and other local artifacts are
now ignored. coverage joins the dev requirements.

.pre-commit-config.yaml

@@ -9,7 +9,7 @@ repos:
 
       - id: flake8
         name: flake8
-        entry: flake8 --select=E9,F63,F7,F82 --show-source --exclude=reference/,web/
+        entry: flake8 --show-source
         language: system
         types: [python]