FINERACT-2711: Fix shared-account template named-range bounds built by string concat

[oluexpert99]

 - SharedAccountWorkBookPopulator.setNames built the Clients and Products named ranges as
    SHEET + "!$B$2:$B$" + list.size() + 1. The whole expression is left-to-right string
    concatenation, so size() + 1 does not add: the "1" is appended as text. With two
    products the range became SharedProducts!$B$2:$B$21 instead of $B$2:$B$3, and likewise
    for the client range.
  - The template still downloads, so this is not a 500; the effect is that both dropdowns
    reference far more rows than exist and the picker is padded with blank entries. On a
    tenant with ten products the bound reads $B$101.
  - Parenthesise both bounds so the arithmetic happens before the concatenation, matching
    every sibling populator (LoanWorkbookPopulator, SavingsWorkbookPopulator and others
    already write (size() + 1)).
  - Add a unit test asserting both named ranges end at $B$2:$B$3 for two clients and two
    products. It fails on the unfixed code with the concatenated bound
    (SharedProducts!$B$2:$B$21). Spies feed setNames controlled client and product counts
    while the real populators write their own (empty) sheets, so the assertion isolates the
    range arithmetic.

Description

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