Rename project board -> column to make the UI less confusing (#30170)

This PR split the `Board` into two parts. One is the struct has been
renamed to `Column` and the second we have a `Template Type`.

But to make it easier to review, this PR will not change the database
schemas, they are just renames. The database schema changes could be in
future PRs.

---------

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: yp05327 <576951401@qq.com>
(cherry picked from commit 98751108b11dc748cc99230ca0fc1acfdf2c8929)

Conflicts:
	docs/content/administration/config-cheat-sheet.en-us.md
	docs/content/index.en-us.md
	docs/content/installation/comparison.en-us.md
	docs/content/usage/permissions.en-us.md
	non existent files

	options/locale/locale_en-US.ini
	routers/web/web.go
	templates/repo/header.tmpl
	templates/repo/settings/options.tmpl
	trivial context conflicts

web_src/css/features/projects.css

@@ -7,7 +7,7 @@
 }
 
 .project-column {
-  background-color: var(--color-project-board-bg) !important;
+  background-color: var(--color-project-column-bg) !important;
   border: 1px solid var(--color-secondary) !important;
   margin: 0 0.5rem !important;
   padding: 0.5rem !important;