Product repository template

Layout, proplan.toml, README/CHANGELOG, placeholder product image, .gitignore, KiBot/release/docgen workflows and TEMPLATE.md. Source of truth: contrib/product-template in B4L/proplan (cargo test --test product_template checks it as Gitea 1.27 creates a repository from it).

hardware/$REPO_NAME/README.md

@@ -0,0 +1,11 @@
+# $REPO_NAME board
+
+The KiCad project of $REPO_NAME lives here: create it with KiCad (File, New
+Project) as `hardware/$REPO_NAME/$REPO_NAME.kicad_pro`.
+
+- A revision of this board is a git tag (`v0.1`), not a copy of this folder.
+- A real variant built next to it (48 V, 2-board) gets its own folder under
+  `hardware/` and its own `[[boards]]` entry in `proplan.toml`.
+- Shared symbols, footprints and 3D models go to `hardware/lib/`.
+- Gerbers, BOMs and PDFs are built by CI (`.gitea/workflows/kibot.yml`); do not
+  commit them.