fix: add TypeScript declarations and fix build errors

Fixed TypeScript compilation errors preventing Docker build:

1. Added type declarations for convert-units library:
   - Created types/convert-units.d.ts with proper interfaces
   - Defined Unit and Converter interfaces
   - Made value parameter optional in convert() function
   - Methods like measures() accessible on Converter instance

2. Fixed CommandPalette type error:
   - Added explicit type annotation to commands array
   - Made color property optional (color?: string)
   - Theme commands don't have color, measure commands do

Build now completes successfully:
- TypeScript compilation passes
- Static pages generate correctly
- Ready for Docker build

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

types/convert-units.d.ts

@@ -0,0 +1,30 @@
+declare module 'convert-units' {
+  export interface Unit {
+    abbr: string;
+    measure: string;
+    system: string;
+    singular: string;
+    plural: string;
+  }
+
+  export interface Converter {
+    from(unit: string): {
+      to(toUnit: string): number;
+      toBest(options?: { exclude?: string[]; cutOffNumber?: number }): {
+        val: number;
+        unit: string;
+        singular: string;
+        plural: string;
+      };
+      getUnit(): Unit;
+      possibilities(): string[];
+    };
+    measures(): string[];
+    possibilities(measure?: string): string[];
+    describe(unit: string): Unit;
+  }
+
+  function convert(value?: number): Converter;
+
+  export default convert;
+}