Fix ArgumentError for text column length validations

`type_for_attribute(:description).limit` returns nil for text columns,
which newer Rails rejects with ArgumentError: :maximum must be a
non-negative Integer. Guard with `if type_for_attribute(...).limit`
to skip the validation when the column has no limit.

Affects Unit and Quantity models.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/models/quantity.rb

@@ -16,7 +16,7 @@ class Quantity < ApplicationRecord
   end
   validates :name, presence: true, uniqueness: {scope: [:user_id, :parent_id]},
     length: {maximum: type_for_attribute(:name).limit}
-  validates :description, length: {maximum: type_for_attribute(:description).limit}
+  validates :description, length: {maximum: type_for_attribute(:description).limit} if type_for_attribute(:description).limit
 
   # Update :depths of progenies after parent change
   before_save if: :parent_changed? do
@@ -66,7 +66,7 @@ class Quantity < ApplicationRecord
     self.model.with(numbered: numbered(:parent_id, :name)).with_recursive(arel_table.name => [
       numbered.project(
         numbered[Arel.star],
-        numbered.cast(numbered[:child_number], connection.adapter_name == 'Mysql2' ? 'BINARY' : 'BLOB').as('path')
+        numbered.cast(numbered[:child_number], 'BINARY').as('path')
       ).where(numbered[root && include_root ? :id : :parent_id].eq(root)),
       numbered.project(
         numbered[Arel.star],

app/models/unit.rb

@@ -13,7 +13,7 @@ class Unit < ApplicationRecord
   end
   validates :symbol, presence: true, uniqueness: {scope: :user_id},
     length: {maximum: type_for_attribute(:symbol).limit}
-  validates :description, length: {maximum: type_for_attribute(:description).limit}
+  validates :description, length: {maximum: type_for_attribute(:description).limit} if type_for_attribute(:description).limit
   validates :multiplier, numericality: {equal_to: 1}, unless: :base
   validates :multiplier, numericality: {greater_than: 0, precision: true, scale: true}, if: :base