Refactor the 12-factor app troubleshooting guide to remove nested tab environments and reduce fragmented, duplicated command examples. The guide now keeps a single Ubuntu base tab set for each task and groups commands that share the same container or invocation. Framework-specific placeholders are normalized to `<app-name>`, while `<framework>` captures the Pebble context where applicable. Legacy Django, Flask, and Spring Boot commands remain separate when their container or Pebble invocation differs. --- - [x] I've followed the [contribution guidelines](https://github.com/canonical/charmcraft/blob/main/CONTRIBUTING.md). - [ ] I've signed the [CLA](http://www.ubuntu.com/legal/contributors/). - [ ] I've successfully run `make lint && make test`. - [x] I've added or updated any relevant documentation. - [x] In documents I changed, I [added a meta description](https://canonical-starflow.readthedocs-hosted.com/how-to/add-a-page-meta-description/) if one was missing. - [ ] I've updated the relevant release notes.