Add the Year in Review developer template (developer-year-review) #248

Part of #5. For "my year in code" posts in December and January.

Idea
The year sits large at the top ("2026") with the person's name next to it. Below are three big stats in a row, each a number with a short label under it ("1,248" commits, "86" pull requests, "TypeScript" top language), and an optional one-line highlight at the bottom ("Shipped my first open source library").

Template details

• File: src/templates/developer/year-review.ts, id developer-year-review
• Fields: name (text), year (text, default "2026"), stat1Value and stat1Label to stat3Value and stat3Label (text), highlight (text, optional), commonFields.bgColor, commonFields.accentColor, commonFields.textColor

Where to look

• Closest reference: src/templates/saas/metric-showcase.ts (a row of big metrics), src/templates/developer/day-streak.ts (numbers with labels, and accent text that stays readable on light backgrounds)

Acceptance criteria

• A stat with an empty value hides and the others share the row, and long values shrink or truncate
• An empty highlight (or only spaces) hides cleanly, and everything stays readable on a light background
• Re-exported in src/templates/developer/index.ts and registered in the Developer block of src/templates/registry.ts
• Meets the shared template checklist in Add new card-style OG image templates #5

One template per contributor at a time, so more people get a chance.

Want to work on this? Comment below and I'll assign it to you. Please take one issue at a time, branch off dev, and open your PR against dev with Closes #248 in the description.