Initialize CBDD solution and add a .NET-focused gitignore for generated artifacts.

.gitignore

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+# .NET build outputs
+[Bb]in/
+[Oo]bj/
+artifacts/
+publish/
+
+# IDE and user settings
+.vs/
+.vscode/
+.idea/
+*.user
+*.rsuser
+*.suo
+*.userprefs
+*.sln.docstates
+
+# NuGet packages
+*.nupkg
+*.snupkg
+packages/
+!packages/build/
+project.lock.json
+project.fragment.lock.json
+
+# Testing and coverage
+TestResults/
+TestResults*/
+coverage/
+coverage*/
+*.trx
+*.coverage
+*.coveragexml
+*.lcov
+BenchmarkDotNet.Artifacts/
+
+# Node.js / web outputs (if applicable)
+node_modules/
+dist/
+build/
+.output/
+.nuxt/
+.cache/
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+.pnpm-debug.log*
+
+# Generated data files and report artifacts
+generated/
+generated-data/
+data/generated/
+output/
+out/
+reports/
+tmp/
+temp/
+*.tmp
+*.temp
+*.bak
+*.pid
+*.seed
+*.dat
+*.csv
+*.tsv
+*.jsonl
+*.ndjson
+*.parquet
+*.feather
+*.arrow
+*.sqlite
+*.sqlite3
+*.db
+*.h5
+*.hdf5
+
+# Environment files
+.env
+.env.local
+.env.*.local
+
+# OS files
+Thumbs.db
+Desktop.ini
+.DS_Store