feat(config): add issue templates for Epics, User Stories, and Subtasks (#4)

Reviewed-on: #4

.gitea/ISSUE_TEMPLATE/user_story.md

@@ -0,0 +1,42 @@
+---
+name: "User Story"
+about: "A feature or requirement from the user's perspective"
+title: "[Story] <User story title>"
+labels: ["Type/User Story"]
+---
+
+## 🧍‍♂️ User Story
+**As a** [type of user]  
+**I want to** [perform an action]  
+**So that** [achieve a goal or value]
+
+---
+
+## 📋 Description
+Provide additional context or business logic for this story.
+
+---
+
+## 🎯 Acceptance Criteria
+List the specific, measurable criteria that define when this story is done:
+- [ ] Criterion 1
+- [ ] Criterion 2
+- [ ] Criterion 3
+
+---
+
+## 🧱 Implementation Notes
+Include technical notes, design references, or constraints.
+
+---
+
+## 🧵 Linked Issues
+- Parent Epic: #<epic-number>
+- Related Subtasks:
+  - [ ] #<subtask-1>
+  - [ ] #<subtask-2>
+
+---
+
+## 🧩 Estimated Size
+Use label: `Size/XS` | `Size/S` | `Size/M` | `Size/L` | `Size/XL`