feat: finish demo — Angular 22 + Material UI, role management, schema and Docker cleanup

Frontend
- Upgrade Angular 19 -> 22 (TypeScript 6, new control flow), drop unused
  packages (bootstrap, jquery, popper, ng-bootstrap, webpack)
- Move the UI to Angular Material: toolbar with user menu, tutorials list,
  add/edit forms, admin users table with role editing dialog, profile,
  home page with published tutorials, registration form, login dialog
- Guard routes: login required for add/edit/profile, admin role for /admin
- Remove the /login, Moderator and User pages, event bus, auth interceptor
  and other dead code

Backend
- Add PUT /api/users/{id}/roles (admin only) that keeps at least one admin
  and does not let an admin drop their own admin role
- Tighten security: read tutorials publicly, change them only when logged
  in, users/roles API for admins only; hide password hashes in JSON
- Remove unused Settings and Test endpoints, DTO mappers, commented code
- Flyway V2 aligns the schema with the entities (bigint ids, tutorials PK,
  identity ids); Hibernate now runs with ddl-auto: validate

Docker
- Three-stage Dockerfile (Node build, Gradle build, JRE runtime) with
  layer caching, non-root user and healthcheck; add .dockerignore
- docker-compose waits for a healthy Postgres, always rebuilds the image,
  no longer mounts the Docker socket

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

spring-angular-ui/src/app/components/home/home.component.html

@@ -1,5 +1,38 @@
-<div class="container">
-    <header class="jumbotron">
-      <p>{{ content }}</p>
-    </header>
-  </div>
+<div class="page">
+  @if (!isLoggedIn) {
+    <div class="demo-banner" role="note">
+      <mat-icon>info</mat-icon>
+      <div>
+        <strong>This is a demo project.</strong>
+        Log in as <code>Admin</code> with password <code>pwd123</code> to try editing tutorials and the admin page.
+      </div>
+    </div>
+  }
+
+  <div class="page-header">
+    <h1 class="page-title">Published tutorials</h1>
+  </div>
+
+  @if (tutorials.length) {
+    <div class="grid">
+      @for (tutorial of tutorials; track tutorial.id) {
+        <mat-card appearance="outlined" class="tutorial-card">
+          <mat-card-header>
+            <mat-icon mat-card-avatar class="card-icon">article</mat-icon>
+            <mat-card-title>{{ tutorial.title }}</mat-card-title>
+          </mat-card-header>
+          <mat-card-content>
+            <p class="description">{{ tutorial.description || 'No description' }}</p>
+          </mat-card-content>
+        </mat-card>
+      }
+    </div>
+  } @else if (loaded) {
+    <mat-card appearance="outlined">
+      <div class="empty">
+        <mat-icon>menu_book</mat-icon>
+        <p>No published tutorials yet</p>
+      </div>
+    </mat-card>
+  }
+</div>

spring-angular-ui/src/app/components/home/home.component.scss

@@ -0,0 +1,49 @@
+@use '../tutorial-shared';
+
+.grid {
+  display: grid;
+  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
+  gap: 16px;
+}
+
+.tutorial-card {
+  height: 100%;
+}
+
+.card-icon {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  background-color: var(--mat-sys-primary-container);
+  color: var(--mat-sys-on-primary-container);
+}
+
+mat-card-content {
+  padding-top: 12px;
+}
+
+.description {
+  margin: 0;
+  white-space: pre-line;
+  color: var(--mat-sys-on-surface-variant);
+}
+
+.demo-banner {
+  display: flex;
+  align-items: flex-start;
+  gap: 12px;
+  margin-bottom: 24px;
+  padding: 16px;
+  border-radius: 12px;
+  font: var(--mat-sys-body-medium);
+  background-color: var(--mat-sys-secondary-container);
+  color: var(--mat-sys-on-secondary-container);
+
+  code {
+    padding: 1px 6px;
+    border-radius: 4px;
+    font-weight: 500;
+    background-color: var(--mat-sys-surface);
+    color: var(--mat-sys-primary);
+  }
+}

spring-angular-ui/src/app/components/home/home.component.ts

@@ -1,25 +1,38 @@
-import { Component, OnInit } from '@angular/core';
-import { UserService } from 'src/app/services/user.service';
+import { ChangeDetectionStrategy, Component, inject, OnInit } from '@angular/core';
+import { MatSnackBar } from '@angular/material/snack-bar';
+
+import { httpErrorMessage } from 'src/app/helpers/http-error';
+import { Tutorial } from 'src/app/models/tutorial.model';
+import { TokenStorageService } from 'src/app/services/token-storage.service';
+import { TutorialService } from 'src/app/services/tutorial.service';
 
 @Component({
-    selector: 'app-home',
-    templateUrl: './home.component.html',
-    styleUrls: ['./home.component.scss'],
-    standalone: false
+  selector: 'app-home',
+  templateUrl: './home.component.html',
+  styleUrls: ['./home.component.scss'],
+  changeDetection: ChangeDetectionStrategy.Eager,
+  standalone: false
 })
 export class HomeComponent implements OnInit {
-  content?: string;
+  private readonly tutorialService = inject(TutorialService);
+  private readonly snackBar = inject(MatSnackBar);
 
-  constructor(private userService: UserService) { }
+  readonly isLoggedIn = inject(TokenStorageService).isLoggedIn();
+
+  tutorials: Tutorial[] = [];
+  loaded = false;
 
   ngOnInit(): void {
-    // this.userService.getPublicContent().subscribe(
-    //   (data : any) => {
-    //     this.content = data;
-    //   },
-    //   (err : any) => {
-    //     this.content = JSON.parse(err.error).message;
-    //   }
-    // );
+    this.tutorialService.getPublished().subscribe({
+      // На пустой результат сервер отвечает 204 без тела
+      next: data => {
+        this.tutorials = data ?? [];
+        this.loaded = true;
+      },
+      error: err => {
+        this.loaded = true;
+        this.snackBar.open(httpErrorMessage(err), 'OK', { duration: 5000 });
+      }
+    });
   }
-}
+}