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>

constants/theme.ts

@@ -1,16 +1,16 @@
 export const Colors = {
-  bg: "#0f1117",
-  surface: "#1a1d27",
-  surface2: "#252836",
-  primary: "#6366f1",
-  primaryDim: "#4338ca",
-  success: "#22c55e",
-  warning: "#f59e0b",
-  danger: "#ef4444",
-  text1: "#f1f5f9",
-  text2: "#94a3b8",
-  textDim: "#64748b",
-  border: "#2d3147",
+  bg: "#1B2433",
+  surface: "#222D3D",
+  surface2: "#293648",
+  primary: "#88D656",
+  primaryDim: "#5FA33A",
+  success: "#88D656",
+  warning: "#F5A623",
+  danger: "#EF4444",
+  text1: "#EEF2F5",
+  text2: "#8FA5BF",
+  textDim: "#4E6480",
+  border: "#2E3F55",
 } as const;
 
 export const FontFamily = {