feat(admin): add Filament resources for the forecasting stack

Adds three resources under a new "Forecasting" navigation group: a full-CRUD
WatchedEventResource for the Layer 5 volatility detector, plus read-only
WeeklyForecastResource and BacktestResource so the ridge model output and
its calibration can be inspected without SQL.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/Filament/NavigationGroup.php

@@ -13,6 +13,8 @@ enum NavigationGroup implements HasIcon, HasLabel
 
     case Data;
 
+    case Forecasting;
+
     case System;
 
     public function getLabel(): string
@@ -20,6 +22,7 @@ enum NavigationGroup implements HasIcon, HasLabel
         return match ($this) {
             self::Users => 'Users',
             self::Data => 'Data',
+            self::Forecasting => 'Forecasting',
             self::System => 'System',
         };
     }
@@ -29,6 +32,7 @@ enum NavigationGroup implements HasIcon, HasLabel
         return match ($this) {
             self::Users => 'heroicon-o-users',
             self::Data => 'heroicon-o-circle-stack',
+            self::Forecasting => null,
             self::System => 'heroicon-o-cog-6-tooth',
         };
     }