Seed from go-template-repo, renamed to simplexcalc

The template's files at a77fd30, without its history or LICENSE, after
script/rename simplexcalc.

Model: opus-5-5

internal/database/schema/001_widgets.sql

@@ -0,0 +1,15 @@
+-- 001_widgets.sql: the example table. Delete it when seeding a real
+-- project and start your own schema at 001 — nothing has been deployed
+-- yet, so there is no ledger anywhere that would disagree.
+--
+-- It is here so that the template's migration runner, model layer and
+-- tests all exercise a real table rather than an empty database.
+
+CREATE TABLE IF NOT EXISTS widgets (
+    id          TEXT PRIMARY KEY,
+    name        TEXT NOT NULL,
+    size_bytes  INTEGER NOT NULL DEFAULT 0,
+    created_at  TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ', 'now'))
+);
+
+CREATE INDEX IF NOT EXISTS widgets_created_at ON widgets (created_at);