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/Features/Students/EventRanking.razor

@@ -2,7 +2,9 @@
 @attribute [Authorize]
 @using Microsoft.EntityFrameworkCore
 @using WebApp.Models
+@using Core.Validation
 @inject AppDbContext Context
+@inject ValidationService ValidationService
 @rendermode InteractiveServer
 
 <PageTitle>Student Event Ranks - TSA Chapter Organizer</PageTitle>
@@ -37,25 +39,7 @@ else
             <MudTh>@context.TsaYear</MudTh>
             <MudTd><MudButton StartIcon="@Icons.Material.Filled.TableChart" Href="@($"students/event-ranking-edit/{context.Id}")">Edit</MudButton></MudTd>
             <MudTd>
-                @if (!context.RankedEvents.Any(re => re.OnSiteActivity))
-                {
-                    <MudTooltip Text="No On-Site Activity">
-                        <MudText Style="font-weight:bolder" Color="Color.Warning">@AppIcons.OnSiteActivity</MudText>
-                    </MudTooltip>
-                }
-                @if (!context.RankedEvents.Any(re => re.RegionalEvent))
-                {
-                    <MudTooltip Text="No Regional Event">
-                        <MudText Style="font-weight:bolder" Color="Color.Warning">@AppIcons.RegionalEvent</MudText>
-                    </MudTooltip>
-                }
-
-                @if (context.RankedEvents.All(re => re.EventFormat != EventFormat.Individual))
-                {
-                    <MudTooltip Text="No Individual Event">
-                        <MudText Style="font-weight:bolder" Color="Color.Warning">@AppIcons.IndividualEvent</MudText>
-                    </MudTooltip>
-                }
+                <ValidationWarnings Warnings="@GetStudentWarnings(context)" />
             </MudTd>
             @for (var i = 1; i <= 10; i++)
             {
@@ -154,4 +138,9 @@ else
 
         _maxEventStudentRankings = _eventStudentRankings.Max(esr => esr.StudentRanking.Length);
     }
+
+    private List<ValidationWarning> GetStudentWarnings(Student student)
+    {
+        return ValidationService.ValidateStudentRankings(student, ValidationContext.StudentRanking);
+    }
 }