✨(project) Django boilerplate

This commit introduces a boilerplate inspired by https://github.com/numerique-gouv/impress.
The code has been cleaned to remove unnecessary Impress logic and dependencies.

Changes made:
- Removed Minio, WebRTC, and create bucket from the stack.
- Removed the Next.js frontend (it will be replaced by Vite).
- Cleaned up impress-specific backend logics.

The whole stack remains functional:
- All tests pass.
- Linter checks pass.
- Agent Connexion sources are already set-up.

Why clear out the code?

To adhere to the KISS principle, we aim to maintain a minimalist codebase. Cloning Impress
allowed us to quickly inherit its code quality tools and deployment configurations for staging,
pre-production, and production environments.

What’s broken?
- The tsclient is not functional anymore.
- Some make commands need to be fixed.
- Helm sources are outdated.
- Naming across the project sources are inconsistent (impress, visio, etc.)
- CI is not configured properly.

This list might be incomplete. Let's grind it.

src/backend/core/admin.py

@@ -0,0 +1,64 @@
+"""Admin classes and registrations for core app."""
+from django.contrib import admin
+from django.contrib.auth import admin as auth_admin
+from django.utils.translation import gettext_lazy as _
+
+from . import models
+
+
+@admin.register(models.User)
+class UserAdmin(auth_admin.UserAdmin):
+    """Admin class for the User model"""
+
+    fieldsets = (
+        (
+            None,
+            {
+                "fields": (
+                    "id",
+                    "admin_email",
+                    "password",
+                )
+            },
+        ),
+        (_("Personal info"), {"fields": ("sub", "email", "language", "timezone")}),
+        (
+            _("Permissions"),
+            {
+                "fields": (
+                    "is_active",
+                    "is_device",
+                    "is_staff",
+                    "is_superuser",
+                    "groups",
+                    "user_permissions",
+                ),
+            },
+        ),
+        (_("Important dates"), {"fields": ("created_at", "updated_at")}),
+    )
+    add_fieldsets = (
+        (
+            None,
+            {
+                "classes": ("wide",),
+                "fields": ("email", "password1", "password2"),
+            },
+        ),
+    )
+    list_display = (
+        "id",
+        "sub",
+        "admin_email",
+        "email",
+        "is_active",
+        "is_staff",
+        "is_superuser",
+        "is_device",
+        "created_at",
+        "updated_at",
+    )
+    list_filter = ("is_staff", "is_superuser", "is_device", "is_active")
+    ordering = ("is_active", "-is_superuser", "-is_staff", "-is_device", "-updated_at")
+    readonly_fields = ("id", "sub", "email", "created_at", "updated_at")
+    search_fields = ("id", "sub", "admin_email", "email")