Update OpenCommit configuration:

- Changed AI provider from 'llama3' to 'mistral'
   - Updated API key and model version for OpenAI
   - Set One Line Commit to true, enabling one-line commit messages
   - Added GitPush and Why options with default values set to false
   - Created backup of previous configuration as .opencommit.backup

.opencommit.backup

@@ -0,0 +1,15 @@
+OCO_MODEL=llama3:latest
+OCO_API_URL=http://localhost:11434/api/chat
+OCO_API_KEY=some-api-key-here
+OCO_AI_PROVIDER=ollama
+OCO_TOKENS_MAX_INPUT=40960
+OCO_TOKENS_MAX_OUTPUT=4096
+OCO_DESCRIPTION=false
+OCO_EMOJI=false
+OCO_LANGUAGE=en
+OCO_MESSAGE_TEMPLATE_PLACEHOLDER=$msg
+OCO_PROMPT_MODULE=conventional-commit
+OCO_ONE_LINE_COMMIT=false
+OCO_TEST_MOCK_TYPE=commit-message
+OCO_GITPUSH=false
+OCO_WHY=false