This PR refactors a bunch of projects-related code, mostly the templates. The following things were done: - rename boards to columns in frontend code - use the new `ctx.Locale.Tr` method - cleanup template, remove useless newlines, classes, comments - merge org-/user and repo level project template together - move "new column" button into project toolbar - move issue card (shared by projects and pinned issues) to shared template, remove useless duplicated styles - add search function to projects (to make the layout more similar to milestones list where it is inherited from 😆) - maybe more changes I forgot I've done 😆 Closes #24893 After: ![Bildschirmfoto vom 2023-08-10 23-02-00](https://github.com/go-gitea/gitea/assets/47871822/cab61456-1d23-4373-8163-e567f1b3b5f9) ![Bildschirmfoto vom 2023-08-10 23-02-26](https://github.com/go-gitea/gitea/assets/47871822/94b55d60-5572-48eb-8111-538a52d8bcc6) ![Bildschirmfoto vom 2023-08-10 23-02-46](https://github.com/go-gitea/gitea/assets/47871822/a0358f4b-4e05-4194-a7bc-6e0ecba5a9b6) --------- Co-authored-by: silverwind <me@silverwind.io>

Merge the repo- and org-level templates into one #24893

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