Refactor project templates (#26448)

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>

web_src/js/features/repo-issue-list.js

@@ -140,7 +140,7 @@ function initRepoIssueListAuthorDropdown() {
 }
 
 function initPinRemoveButton() {
-  for (const button of document.getElementsByClassName('pinned-issue-unpin')) {
+  for (const button of document.getElementsByClassName('issue-card-unpin')) {
     button.addEventListener('click', async (event) => {
       const el = event.currentTarget;
       const id = Number(el.getAttribute('data-issue-id'));
@@ -157,7 +157,7 @@ function initPinRemoveButton() {
         // Delete the tooltip
         el._tippy.destroy();
         // Remove the Card
-        el.closest(`div.pinned-issue-card[data-issue-id="${id}"]`).remove();
+        el.closest(`div.issue-card[data-issue-id="${id}"]`).remove();
       }
     });
   }