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/appsettings.json

@@ -17,5 +17,23 @@
     "StateId": "00000",
     "RegionalId": "00000",
     "CompetitionYear": "2026"
+  },
+  "ValidationSettings": {
+    "MinRecommendedEvents": 2,
+    "MaxRecommendedEvents": 4,
+    "MinCriticalEvents": 1,
+    "MaxCriticalEvents": 6,
+    "MaxRegionalEvents": 3,
+    "RequireRegionalEvent": true,
+    "RequireOnSiteActivity": true,
+    "RequireIndividualEvent": false,
+    "RequireTeamCaptain": true,
+    "NoRegionalEventSeverity": "Warning",
+    "NoOnSiteActivitySeverity": "Warning",
+    "NoIndividualEventSeverity": "Warning",
+    "TeamSizeSeverity": "Warning",
+    "EventCountSeverity": "Warning",
+    "MissingCaptainSeverity": "Warning",
+    "TooManyRegionalEventsSeverity": "Warning"
   }
 }