fix(ssr): apply theme CSS vars during SSR and enable client hydration

- ThemeService: remove isPlatformBrowser guard so CSS custom properties
  are applied during SSR/prerender — server-rendered HTML now carries the
  correct color scheme and gradients (fixes missing colors on test site).

- main.ts: add provideClientHydration() so Angular preserves the server-
  rendered DOM on the client instead of destroying and rebuilding it
  (fixes jarring full-page reload between static and dynamic versions).

- Tests: update theme.service.spec.ts to match new behaviour, expand
  coverage with gradient tests and empty-value handling (9 tests).
  Fix structured-data.component.spec.ts import paths. All 54 tests pass.

server.spec.ts

@@ -0,0 +1,90 @@
+// Load the JIT compiler BEFORE any Angular router/common imports
+import '@angular/compiler';
+
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+
+// Mock the @angular/ssr/node imports that pull in Node.js http server code
+// — we only want to test PRERENDERED_ROUTES and isPrerenderedRoute here.
+vi.mock('@angular/ssr/node', () => ({
+  AngularNodeAppEngine: class {},
+  createNodeRequestHandler: (fn: Function) => fn,
+  isMainModule: () => false,
+  writeResponseToNodeResponse: vi.fn(),
+}));
+
+vi.mock('node:http', () => ({
+  default: { createServer: vi.fn() },
+}));
+
+import { PRERENDERED_ROUTES, isPrerenderedRoute } from './server';
+
+describe('SSR server — server.ts', () => {
+  describe('PRERENDERED_ROUTES', () => {
+    it('should contain exactly 5 routes', () => {
+      expect(PRERENDERED_ROUTES).toHaveLength(5);
+    });
+
+    it('should include the home route', () => {
+      expect(PRERENDERED_ROUTES).toContain('/');
+    });
+
+    it('should include /about', () => {
+      expect(PRERENDERED_ROUTES).toContain('/about');
+    });
+
+    it('should include /schedule', () => {
+      expect(PRERENDERED_ROUTES).toContain('/schedule');
+    });
+
+    it('should include /events', () => {
+      expect(PRERENDERED_ROUTES).toContain('/events');
+    });
+
+    it('should include /contact', () => {
+      expect(PRERENDERED_ROUTES).toContain('/contact');
+    });
+  });
+
+  describe('isPrerenderedRoute()', () => {
+    it('should match exact prerendered paths', () => {
+      expect(isPrerenderedRoute('/')).toBe(true);
+      expect(isPrerenderedRoute('/about')).toBe(true);
+      expect(isPrerenderedRoute('/schedule')).toBe(true);
+      expect(isPrerenderedRoute('/events')).toBe(true);
+      expect(isPrerenderedRoute('/contact')).toBe(true);
+    });
+
+    it('should match paths with trailing slashes', () => {
+      expect(isPrerenderedRoute('/about/')).toBe(true);
+      expect(isPrerenderedRoute('/schedule/')).toBe(true);
+      expect(isPrerenderedRoute('/events/')).toBe(true);
+      expect(isPrerenderedRoute('/contact/')).toBe(true);
+    });
+
+    it('should match paths with query strings', () => {
+      expect(isPrerenderedRoute('/about?foo=bar')).toBe(true);
+      expect(isPrerenderedRoute('/schedule?day=monday')).toBe(true);
+    });
+
+    it('should match paths with fragments', () => {
+      expect(isPrerenderedRoute('/events#upcoming')).toBe(true);
+    });
+
+    it('should reject non-prerendered routes', () => {
+      expect(isPrerenderedRoute('/login')).toBe(false);
+      expect(isPrerenderedRoute('/admin')).toBe(false);
+      expect(isPrerenderedRoute('/nonexistent')).toBe(false);
+      expect(isPrerenderedRoute('/admin/dashboard')).toBe(false);
+    });
+
+    it('should handle full URLs', () => {
+      expect(isPrerenderedRoute('https://kmtnflower.org/about')).toBe(true);
+      expect(isPrerenderedRoute('http://localhost:4200/events')).toBe(true);
+      expect(isPrerenderedRoute('https://kmtnflower.org/login')).toBe(false);
+    });
+
+    it('should normalise root path — "/" stays "/"', () => {
+      expect(isPrerenderedRoute('/')).toBe(true);
+    });
+  });
+});