standardize UI colors to fit brand guidelines (#3754)

## Description:

We have brand colors:

<img width="738" height="900" alt="Screenshot 2026-04-25 at 12 52 29 PM"
src="https://github.com/user-attachments/assets/aac69e87-91f2-4c3f-9f1e-f69f48f5943e"
/>

So update the homepage & in-game UI to use those colors:

<img width="1185" height="946" alt="Screenshot 2026-04-25 at 12 51
06 PM"
src="https://github.com/user-attachments/assets/89a0b12c-2db1-43d4-9500-fcf405c0f7ff"
/>

Also updated buttons to use the o-button element

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

## Please put your Discord username so you can be contacted if a bug or
regression is found:

evan

src/client/TroubleshootingModal.ts

@@ -46,12 +46,12 @@ export class TroubleshootingModal extends BaseModal {
               >
               / ${translateText("troubleshooting.title")}
             </span>
-            <button
-              class="hover:bg-white/5 px-6 py-2 text-xs font-bold transition-all duration-200 rounded-lg uppercase tracking-widest bg-blue-500/20 text-blue-400 border border-blue-500/30 shadow-[0_0_15px_rgba(59,130,246,0.2)]"
+            <o-button
+              variant="primary"
+              size="sm"
+              translationKey="common.copy"
               @click=${this.copyDiagnostics}
-            >
-              ${translateText("common.copy")}
-            </button>
+            ></o-button>
           </div>`,
           onBack: () => this.close(),
           ariaLabel: translateText("common.back"),