Add comprehensive validation system with runtime configuration

Implements a flexible validation framework for student rankings, team assignments, and team composition with administrator-configurable rules and thresholds.

Validation System:
- Reflection-based rule discovery eliminates manual registration
- Base classes (RequiredEventTypeRuleBase, EventCountThresholdRuleBase) reduce code duplication by ~250 lines
- 12 validation rules covering event requirements, counts, and team constraints
- Configurable severity levels (Warning/Error) per rule type
- ValidationService with caching for optimal performance
- Rules apply contextually (StudentRanking, StudentAssignment, TeamComposition)

Configuration & Admin UI:
- ValidationSettings admin page for editing thresholds and severity levels
- ChapterSettings admin page for editing chapter information
- Settings stored in Data/appsettings.json for runtime configuration
- JSON config works in both development and production environments
- Auto-creates Data directory and config template on first run

User Experience:
- ValidationWarnings component displays inline warnings/errors
- Integrated in Event Ranking, Registration, and Team Assignment pages
- Color-coded severity indicators (warning yellow, error red)
- Includes "Too Many Regional Events" rule (max 3 recommended)

Technical Improvements:
- Template Method pattern for rule base classes
- Singleton rule instances with lazy initialization
- Configuration loaded via IConfiguration with fallback to defaults
- Safe JSON updates preserve other appsettings sections

WebApp/Components/Shared/ValidationWarnings.razor

@@ -0,0 +1,37 @@
+@using Core.Validation
+@using WebApp.Models
+
+@if (Warnings != null && Warnings.Any())
+{
+    <MudText Style="display: inline-flex; gap: 4px;">
+        @foreach (var warning in Warnings)
+        {
+            var color = warning.Severity == ValidationSeverity.Error ? Color.Error : Color.Warning;
+            var icon = GetIconFromIdentifier(warning.IconIdentifier);
+
+            <MudTooltip Text="@warning.Message">
+                <MudText Style="font-weight:bolder" Color="@color">@icon</MudText>
+            </MudTooltip>
+        }
+    </MudText>
+}
+
+@code {
+    [Parameter]
+    public List<ValidationWarning>? Warnings { get; set; }
+
+    private string GetIconFromIdentifier(string? identifier)
+    {
+        if (string.IsNullOrEmpty(identifier))
+            return "";
+
+        return identifier switch
+        {
+            "RegionalEvent" => AppIcons.RegionalEvent,
+            "OnSiteActivity" => AppIcons.OnSiteActivity,
+            "IndividualEvent" => AppIcons.IndividualEvent,
+            "Captain" => AppIcons.Captain,
+            _ => ""
+        };
+    }
+}