feat(svg): add 2D GitHub-style heatmap view (JhaSourav07#1915)

## Description

Introduces a new `view=heatmap` URL parameter that renders a premium,
flat 2D GitHub-style contribution heatmap as an SVG badge.
This provides a cleaner, traditional alternative to the default 3D
isometric monolith while maintaining CommitPulse's high aesthetic
standards.

**Key Features Included:**
- 14-week contribution grid with 5 color intensity levels based on
contribution quartiles.
- Smooth scan-line sweep animation and a pulsing border for "today's"
cell.
- Glow effects on peak contribution days (intensity level 4).
- Full compatibility with existing parameters (themes, `auto` theme,
`size`, `hide_background`, `hide_stats`, `lang`).
- Updated `README.md` documentation and copy examples for the new view.
- Added `'heatmap'` to the Zod validation schema and `BadgeParams.view`
types.

Fixes JhaSourav07#1914 

## Pillar

- [x] 🎨 Pillar 1 — New Theme Design
- [x] 📐 Pillar 2 — Geometric SVG Improvement
- [ ] 🕐 Pillar 3 — Timezone Logic Optimization
- [ ] 🛠️ Other (Bug fix, refactoring, docs)

## Visual Preview
<img width="1869" height="919" alt="image"
src="https://github.com/user-attachments/assets/7da63c67-63d9-49ee-a52f-3bd67dee3d94"
/>

## 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.,
`feat(themes): ...`, `fix(calculate): ...`).
- [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

README.md

@@ -176,7 +176,7 @@ URL Parameter > Theme Default > System Fallback
 | `hide_stats`      | `boolean` | No         | `false`                        | Hides the bottom row displaying Current Streak, Annual Sync Total, and Peak Streak stats when set to `true` or `1`.                                                       |
 | `tz`              | `string`  | No         | Omitted = UTC                  | IANA timezone (e.g. `Asia/Kolkata`, `America/New_York`) — aligns "today" with the user local midnight. Note: `?tz=UTC` is valid but cached separately from omitting `tz`. |
 | `lang`            | `string`  | No         | `en`                           | Language code for labels (`en`, `es`, `hi`, `fr`, `pt`, `ko`, `ja`, `de`, `zh`)                                                                                           |
-| `view`            | `string`  | No         | `default`                      | Rendering mode: `default` (3D Monolith) or `monthly` (Compact monthly stats)                                                                                              |
+| `view`            | `string`  | No         | `default`                      | Rendering mode: `default` (3D Monolith), `monthly` (Compact monthly stats), or `heatmap` (flat 2D contribution heatmap)                                                   |
 | `delta_format`    | `string`  | No         | `percent`                      | Format for month-over-month delta in monthly view: `percent` (e.g. +12%), `absolute` (e.g. +15 commits), or `both`                                                        |
 | `width`           | `number`  | No         | `300`                          | Custom width for the SVG canvas (currently only applies to `view=monthly`)                                                                                                |
 | `height`          | `number`  | No         | `120`                          | Custom height for the SVG canvas (currently only applies to `view=monthly`)                                                                                               |
@@ -319,6 +319,14 @@ Explore some of the built-in CommitPulse themes and quickly copy the style you l
 <!-- Gradient + shading for extra depth -->
 
 ![](https://commitpulse.vercel.app/api/streak?user=jhasourav07&gradient=true&shading=true)
+
+<!-- GitHub-style Heatmap View -->
+
+![](https://commitpulse.vercel.app/api/streak?user=jhasourav07&view=heatmap)
+
+<!-- Heatmap with Neon theme -->
+
+![](https://commitpulse.vercel.app/api/streak?user=jhasourav07&view=heatmap&theme=neon)
 ```
 
 ---

app/api/streak/route.ts

@@ -9,6 +9,7 @@ import {
   generateSVG,
   generateMonthlySVG,
   generateVersusSVG,
+  generateHeatmapSVG,
 } from '@/lib/svg/generator';
 import { getSecondsUntilUTCMidnight, getSecondsUntilMidnightInTimezone } from '@/utils/time';
 import type { BadgeParams } from '@/types';
@@ -197,6 +198,9 @@ export async function GET(request: Request) {
         getMonthlyReferenceDate(year, timezone)
       );
       svg = generateMonthlySVG(stats, params);
+    } else if (view === 'heatmap') {
+      const stats = calculateStreak(calendar, timezone, undefined, grace);
+      svg = generateHeatmapSVG(stats, params, calendar);
     } else if (versus && versusCalendar) {
       const stats1 = calculateStreak(calendar, timezone, undefined, grace);
       const stats2 = calculateStreak(versusCalendar, timezone, undefined, grace);