refactor(github): move achievement milestones to config file (JhaSourav07#556)

## Description

Fixes JhaSourav07#312

## Pillar
- [x] 🛠️ Other (Bug fix, refactoring, docs)

## Visual Preview
*No visual changes (Pure architectural code refactoring).*

## Checklist before requesting a review:

- [x] I have read the `CONTRIBUTING.md` file.
- [x] I have tested these changes locally
(`localhost:3000/api/streak?user=YOUR_USERNAME`).
- [x] I have run `npm run format` and `npm run lint` locally and
resolved all errors (CI will fail otherwise).
- [x] My commits follow the Conventional Commits format (e.g.,
`refactor(github): ...`).
- [x] I have updated `README.md` if I added a new theme or URL
parameter.
- [x] I have starred the repo.
- [x] I have made sure that i have only one commit to merge in this PR.
- [x] The SVG output matches the CommitPulse "premium quality" aesthetic
standard (no raw elements, smooth animations, correct fonts).
- [x] (Recommended) I joined the CommitPulse Discord community for
contributor discussions, mentorship, and faster PR support.

Author: JhaSourav07

lib/github.ts

@@ -4,6 +4,7 @@ import type { ContributionCalendar, ContributionDay } from '@/types';
 import { calculateStreak, aggregateCalendars, calculateWrappedStats } from '@/lib/calculate';
 import { TTLCache } from '@/lib/cache';
 import { LANGUAGE_COLORS } from '@/lib/svg/languageColors';
+import { CONTRIBUTION_MILESTONES, STREAK_MILESTONES } from './svg/constants';
 
 interface GitHubRepo {
   stargazers_count: number;
@@ -12,10 +13,8 @@ interface GitHubRepo {
 
 const MAX_RETRIES = 3;
 const BASE_DELAY_MS = 500;
-const CONTRIBUTION_MILESTONES = [1, 10, 100, 250, 500, 1000];
-const STREAK_MILESTONES = [3, 7, 30, 100];
-const GRAPHQL_TIMEOUT_MS = 8000;
-const REST_TIMEOUT_MS = 5000;
+const GRAPHQL_TIMEOUT_MS = 8000; // 8s for GraphQL endpoint
+const REST_TIMEOUT_MS = 5000; // 5s for REST endpoints
 
 export async function fetchWithRetry(
   url: string | URL,

lib/svg/constants.ts

@@ -0,0 +1,17 @@
+export const SVG_WIDTH = 600;
+export const SVG_HEIGHT = 420;
+
+export const GHOST_HEIGHT_PX = 4;
+export const LOG_SCALE_MULTIPLIER = 12;
+export const LINEAR_SCALE_MULTIPLIER = 5;
+export const MAX_LOG_HEIGHT = 80;
+export const MAX_LINEAR_HEIGHT = 50;
+
+export const FONT_MAP: Record<string, string> = {
+  jetbrains: '"JetBrains Mono", monospace',
+  fira: '"Fira Code", monospace',
+  roboto: '"Roboto", sans-serif',
+};
+
+export const CONTRIBUTION_MILESTONES = [1, 10, 100, 250, 500, 1000];
+export const STREAK_MILESTONES = [3, 7, 30, 100];