feat: apply Charbon·Lime design system, add gear icon, multi-provider git settings

- Replace app icon with new Charbon·Lime brand assets (icon.png + adaptive-icon.png)
- Apply design tokens to theme.ts: bg #1B2433, primary/success #88D656 (lime), text1 #EEF2F5 (cream)
- Add ⚙ gear button (lime) in HomeScreen header → navigates to /settings
- Expand settings: git provider selector (Gitea / GitHub / GitLab) with per-provider fields
- Add lib/git.ts: unified pushIncidentToGit() for Gitea, GitHub (PUT), and GitLab APIs
- Update incident detail screen to use lib/git.ts and dynamic provider routing

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

app/index.tsx

@@ -100,7 +100,7 @@ export default function HomeScreen() {
                     backgroundColor:
                       item.status === "open"
                         ? "#f59e0b20"
-                        : "#22c55e20",
+                        : "#88D65620",
                     borderRadius: 4,
                     paddingHorizontal: 8,
                     paddingVertical: 2,