fix(api): pass gradient_stops and gradient_dir through validation and… (JhaSourav07#2244)

## Description

Fixes JhaSourav07#2238 

Custom gradient colors passed via `gradient_stops` and `gradient_dir`
URL parameters were silently ignored, causing the badge to always render
with the default blue gradient.

This PR fixes the issue by:

- Adding `gradient_stops` and `gradient_dir` to `streakParamsSchema` in
`lib/validations.ts`, preventing them from being stripped during Zod
validation.
- Destructuring both fields from `parseResult.data` and passing them
into the `BadgeParams` object in `app/api/streak/route.ts`.
- Calling `generateCustomGradients(params)` before `renderTowers()` in
`lib/svg/generator.ts` so `params.__customGradientId` is populated
before tower rendering begins.

## Pillar

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

## Visual Preview
<img width="1614" height="1007" alt="image"
src="https://github.com/user-attachments/assets/3db5ed79-2b78-4d94-83a7-6ab65dcd20bb"
/>

## 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): ...`).
- [ ] I have updated `README.md` if I added a new theme or URL
parameter.
- [X] I have started 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

app/api/streak/route.ts

@@ -91,6 +91,8 @@ export async function GET(request: Request) {
       versus,
       shading,
       gradient,
+      gradient_stops,
+      gradient_dir,
       opacity,
       tz: tzParam,
       disable_particles,
@@ -173,6 +175,8 @@ export async function GET(request: Request) {
       versus,
       shading,
       gradient,
+      gradient_stops,
+      gradient_dir,
       opacity,
       disable_particles,
       glow,

lib/svg/generator.ts

@@ -646,6 +646,9 @@ export function generateSVG(
     computeTowers(calendar, params.scale, stats.todayDate, params.mode),
     sf
   );
+  if (params.gradient) {
+    generateCustomGradients(params);
+  }
   const towers = renderTowers(
     towerData,
     params,

lib/validations.ts

@@ -308,6 +308,8 @@ const baseStreakParamsSchema = z.object({
       return val === 'true';
     })
     .default(false),
+  gradient_stops: z.string().optional(),
+  gradient_dir: z.enum(['vertical', 'horizontal', 'diagonal']).catch('vertical').optional(),
   disable_particles: z
     .string()
     .optional()