feat: add backend, database, and protocol foundations

sqlc.yaml

@@ -0,0 +1,28 @@
+version: "2"
+sql:
+  - engine: postgresql
+    schema: db/migrations
+    queries: db/queries
+    gen:
+      go:
+        package: query
+        out: internal/adapter/out/postgres/internal/query
+        sql_package: pgx/v5
+        omit_unused_structs: true
+        emit_pointers_for_null_types: true
+        initialisms: [id, url]
+        overrides:
+          - db_type: uuid
+            go_type: string
+          - db_type: uuid
+            nullable: true
+            go_type:
+              type: string
+              pointer: true
+          - db_type: timestamptz
+            go_type: time.Time
+          - db_type: timestamptz
+            nullable: true
+            go_type:
+              type: time.Time
+              pointer: true