[06] Port the Mercosul licence-plate JPEG renderer

[jvwaldrich0]

Task 06 of 16 — these are sequential, do them in order.

Previous: #8 · Next: #10

Port target: cloudpark-toolkit (Go) → this repo (Rust). Reference paths below are relative to that repo.

Goal

Port the Mercosul licence-plate image renderer — the OCR emulator (task 08) sends it as the detection snapshot.

Scope

• Render a Brazilian Mercosul plate (ABC1D23) as a JPEG, 720 px wide, matching the Go layout: blue header band, white body, black bold monospace glyphs.
• Embed the font in the binary (include_bytes! a mono bold TTF); no runtime font lookup.
• Public API: plate::render(text: &str) -> Result<Vec<u8>> (JPEG bytes).
• Crates: image + ab_glyph/rusttype.

Reference

cloudpark-toolkit/internal/plate/render.go (89 lines)

Done when

• Unit test: render("ABC1D23") returns bytes that decode as a valid 720 px JPEG.
• Lowercase/short input is normalised rather than panicking.