fix: resolve Pydantic date field shadowing causing 422 on event update

The field name 'date' in EventUpdate shadowed the 'date' type from
datetime, causing Pydantic v2 to interpret Optional[date] as
Optional[None] — rejecting all non-null values with a 422 error.

Fix: rename import to 'date as _date' and use '_date' in all
annotations. Also improve error handling in admin forms to properly
display 422 validation error messages.

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

src/app/admin/admin-tier-form.component.ts

@@ -0,0 +1,102 @@
+import { Component, EventEmitter, inject, Input, OnChanges, Output, SimpleChanges } from '@angular/core';
+import { CommonModule } from '@angular/common';
+import { FormsModule } from '@angular/forms';
+import { firstValueFrom } from 'rxjs';
+
+import { Tier } from '../interfaces/tier';
+import { TierService } from '../services/tier.service';
+
+@Component({
+  selector: 'app-admin-tier-form',
+  standalone: true,
+  imports: [CommonModule, FormsModule],
+  templateUrl: './admin-tier-form.component.html',
+  styleUrl: './admin-tier-form.component.scss',
+})
+export class AdminTierFormComponent implements OnChanges {
+  private tierService = inject(TierService);
+
+  @Input() editItem: Tier | null = null;
+  @Output() saved = new EventEmitter<void>();
+  @Output() closed = new EventEmitter<void>();
+
+  id: number | null = null;
+  name = '';
+  amount = 0;
+  icon = '⭐';
+  benefits_text = '';
+  display_order = 1;
+
+  loading = false;
+  error = '';
+  submitted = false;
+
+  ngOnChanges(changes: SimpleChanges): void {
+    if (changes['editItem'] && this.editItem) {
+      this.edit(this.editItem);
+    }
+  }
+
+  edit(tier: Tier): void {
+    this.id = tier.id;
+    this.name = tier.name;
+    this.amount = tier.amount;
+    this.icon = tier.icon;
+    this.benefits_text = tier.benefits.join(', ');
+    this.display_order = tier.display_order;
+  }
+
+  reset(): void {
+    this.id = null;
+    this.name = '';
+    this.amount = 0;
+    this.icon = '⭐';
+    this.benefits_text = '';
+    this.display_order = 1;
+    this.error = '';
+    this.submitted = false;
+  }
+
+  onClose(): void {
+    this.closed.emit();
+    this.reset();
+  }
+
+  async onSubmit(): Promise<void> {
+    this.submitted = true;
+    if (!this.name || this.amount <= 0) {
+      this.error = 'Please fill in all required fields.';
+      return;
+    }
+
+    this.loading = true;
+    this.error = '';
+
+    const benefits = this.benefits_text
+      .split(',')
+      .map((b) => b.trim())
+      .filter((b) => b.length > 0);
+
+    const payload = {
+      name: this.name,
+      amount: this.amount,
+      icon: this.icon,
+      benefits: benefits,
+      display_order: this.display_order,
+    };
+
+    try {
+      if (this.id) {
+        await firstValueFrom(this.tierService.updateTier(this.id, payload));
+      } else {
+        await firstValueFrom(this.tierService.createTier(payload));
+      }
+      this.saved.emit();
+      this.reset();
+    } catch (err: any) {
+      this.error = this.formatError(err);
+    } finally {
+      this.loading = false;
+    }
+  }
+}