Add sqlc configuration and core queries

sqlc.yaml (sqlite, schema migrations/, queries migrations/queries/)
generates internal/db with emit_interface. Queries cover dinners (create,
get, list by status, update, archive, set favorite), recipes with
ingredients and steps (upsert by source_url, get, replace children),
photos (insert, get by sha256) and get/upsert for the five settings
singletons. Repository tests run every query against a migrated temp
database.

make sqlc regenerates with the pinned sqlc v1.31.1 (dev tool only, not in
go.mod); make sqlc-check regenerates and fails on any drift in
internal/db, and CI runs it after make test.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

migrations/queries/photos.sql

@@ -0,0 +1,17 @@
+-- name: CreatePhoto :one
+INSERT INTO photos (
+	id, source_url, local_path, width, height, sha256, fetched_at,
+	created_at, updated_at
+) VALUES (
+	?, ?, ?, ?, ?, ?, ?,
+	?, ?
+)
+RETURNING *;
+
+-- name: GetPhotoBySHA256 :one
+-- Finds stored image bytes by content hash. The schema does not make sha256
+-- unique, so the earliest-created (lowest id) match is returned.
+SELECT * FROM photos
+WHERE sha256 = ?
+ORDER BY id
+LIMIT 1;