chore: code quality audit and lint fixes

- Fix all 63 ESLint errors across codebase
- Consolidate MaterialWithTextureSlots type in src/types/three/three.ts
- Add CSS custom properties for design tokens
- Extract ebike constants to src/data/ebike/ebikeConfig.ts
- Add proper TypeScript types for window extensions
- Fix React hooks violations (refs during render, setState in effects)
- Remove unused exports and redundant CSS
- Add type guards for Three.js material handling
- Clean up AI slop comments and legacy CSS patterns

src/pathfinding/useGPS.ts

@@ -38,8 +38,6 @@ export function useGPS({
   // Initialize the pathfinding grid
   useEffect(() => {
     let active = true;
-    setLoading(true);
-    setError(null);
 
     async function initGrid() {
       try {
@@ -63,9 +61,13 @@ export function useGPS({
           colorMapImgRef.current = colorMapImg;
           setLoading(false);
         }
-      } catch (err: any) {
+      } catch (err: unknown) {
         if (active) {
-          setError(err.message || "Failed to initialize GPS system");
+          const message =
+            err instanceof Error
+              ? err.message
+              : "Failed to initialize GPS system";
+          setError(message);
           setLoading(false);
         }
       }

src/pathfinding/useWaypointGPS.ts

@@ -23,8 +23,6 @@ export function useWaypointGPS({
   // Load waypoint list and background color map image
   useEffect(() => {
     let active = true;
-    setLoading(true);
-    setError(null);
 
     async function initGPS() {
       try {
@@ -49,9 +47,13 @@ export function useWaypointGPS({
           colorMapImgRef.current = colorMapImg;
           setLoading(false);
         }
-      } catch (err: any) {
+      } catch (err: unknown) {
         if (active) {
-          setError(err.message || "Failed to initialize Waypoint GPS");
+          const message =
+            err instanceof Error
+              ? err.message
+              : "Failed to initialize Waypoint GPS";
+          setError(message);
           setLoading(false);
         }
       }