fix: resolve TypeScript build errors in map layer expression constants

Add explicit ExpressionSpecification type annotations to MapLibre
expression arrays in GccWatchLayer and MilitaryBasesLayer.

Removing `as const` from the arrays caused them to be inferred as
`(string | string[])[]` which is incompatible with MapLibre's mutable
tuple type. Annotating with `ExpressionSpecification` satisfies the
type checker and produces a clean production build.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Syntax-Error-1337

client/src/modules/monitor/components/GccWatchLayer.tsx

@@ -1,5 +1,6 @@
 import { useMemo } from 'react';
 import { Source, Layer } from 'react-map-gl/maplibre';
+import type { ExpressionSpecification } from 'maplibre-gl';
 import {
   GCC_COUNTRIES,
   useGccCountryAlerts,
@@ -40,7 +41,7 @@ const REGION_CENTROIDS: Record<string, [number, number]> = {
   'al-wusta': [56.82, 21.53],
 };
 
-const FILL_COLOR = [
+const FILL_COLOR: ExpressionSpecification = [
   'case',
   ['==', ['get', 'alertSeverity'], 'warning'],
   'rgba(239, 68, 68, 0.18)',
@@ -49,9 +50,9 @@ const FILL_COLOR = [
   ['==', ['get', 'alertSeverity'], 'advisory'],
   'rgba(234, 179, 8, 0.12)',
   'rgba(96, 165, 250, 0.06)',
-] as const;
+];
 
-const OUTLINE_COLOR = [
+const OUTLINE_COLOR: ExpressionSpecification = [
   'case',
   ['==', ['get', 'alertSeverity'], 'warning'],
   'rgba(239, 68, 68, 0.75)',
@@ -60,25 +61,25 @@ const OUTLINE_COLOR = [
   ['==', ['get', 'alertSeverity'], 'advisory'],
   'rgba(234, 179, 8, 0.60)',
   'rgba(148, 163, 184, 0.20)',
-] as const;
+];
 
-const HALO_COLOR = [
+const HALO_COLOR: ExpressionSpecification = [
   'case',
   ['==', ['get', 'alertSeverity'], 'warning'],
   'rgba(239, 68, 68, 0.14)',
   ['==', ['get', 'alertSeverity'], 'watch'],
   'rgba(251, 146, 60, 0.12)',
   'rgba(234, 179, 8, 0.10)',
-] as const;
+];
 
-const DOT_COLOR = [
+const DOT_COLOR: ExpressionSpecification = [
   'case',
   ['==', ['get', 'alertSeverity'], 'warning'],
   'rgba(239, 68, 68, 0.92)',
   ['==', ['get', 'alertSeverity'], 'watch'],
   'rgba(251, 146, 60, 0.92)',
   'rgba(234, 179, 8, 0.90)',
-] as const;
+];
 
 function CountryLayer({ country }: { country: GccCountry }) {
   const { data: alerts } = useGccCountryAlerts(country);

client/src/modules/monitor/components/MilitaryBasesLayer.tsx

@@ -1,12 +1,13 @@
 import { useMemo } from 'react';
 import { Source, Layer } from 'react-map-gl/maplibre';
+import type { ExpressionSpecification } from 'maplibre-gl';
 import { useMilitaryBases } from '../hooks/useMilitaryBases';
 import { useMilitaryBasesStore } from '../militaryBases.store';
 
 export const MILITARY_BASES_LAYER_IDS = ['military-bases-halo', 'military-bases-dot'];
 
 // MapLibre expression — color by category
-const CATEGORY_COLOR = [
+const CATEGORY_COLOR: ExpressionSpecification = [
   'match',
   ['get', 'category'],
   'air',
@@ -16,9 +17,9 @@ const CATEGORY_COLOR = [
   'ground',
   '#4ade80', // green-400
   '#fbbf24', // amber-400 (hq / default)
-] as const;
+];
 
-const CATEGORY_HALO = [
+const CATEGORY_HALO: ExpressionSpecification = [
   'match',
   ['get', 'category'],
   'air',
@@ -28,7 +29,7 @@ const CATEGORY_HALO = [
   'ground',
   'rgba(74,  222, 128, 0.15)',
   'rgba(251, 191, 36,  0.15)',
-] as const;
+];
 
 /**
  * Renders global military installations on the map,