feat!: Abusive content reporting (#6977)

This implements milestones 1. and 4. from **Task F. Moderation features: Reporting** (part of [amendment of the workplan](https://codeberg.org/forgejo/sustainability/src/branch/main/2022-12-01-nlnet/2025-02-07-extended-workplan.md#task-f-moderation-features-reporting) for NLnet 2022-12-035):

> 1. A reporting feature is implemented in the database. It ensures that content remains available for review, even if a user deletes it after a report was sent.

> 4. Users can report the most relevant content types (at least: issue comments, repositories, users)

### See also:
- forgejo/discussions#291
- forgejo/discussions#304
- forgejo/design#30

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/6977
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Reviewed-by: Otto <otto@codeberg.org>
Co-authored-by: floss4good <floss4good@disroot.org>
Co-committed-by: floss4good <floss4good@disroot.org>

templates/shared/user/profile_big_avatar.tmpl

@@ -123,6 +123,11 @@
 					</button>
 				{{end}}
 			</li>
+			{{if .IsModerationEnabled}}
+			<li class="report">
+				<a class="ui basic orange button" href="{{AppSubUrl}}/report_abuse?type=user&id={{.ContextUser.ID}}">{{ctx.Locale.Tr "moderation.report_abuse"}}</a>
+			</li>
+			{{end}}
 			{{end}}
 		</ul>
 	</div>