chore: Clean up report & knowledge base policies (#11234)

- Removes the portal_members table and all associated records
- Updates policies to use custom roles with knowledge_base_manage
permission
- Updates controllers, models, and views to work without portal
membership
- Adds tests for the new permission model

app/models/account.rb

@@ -2,20 +2,19 @@
 #
 # Table name: accounts
 #
-#  id                         :integer          not null, primary key
-#  auto_resolve_duration      :integer
-#  contactable_contacts_count :integer          default(0)
-#  custom_attributes          :jsonb
-#  domain                     :string(100)
-#  feature_flags              :bigint           default(0), not null
-#  internal_attributes        :jsonb            not null
-#  limits                     :jsonb
-#  locale                     :integer          default("en")
-#  name                       :string           not null
-#  status                     :integer          default("active")
-#  support_email              :string(100)
-#  created_at                 :datetime         not null
-#  updated_at                 :datetime         not null
+#  id                    :integer          not null, primary key
+#  auto_resolve_duration :integer
+#  custom_attributes     :jsonb
+#  domain                :string(100)
+#  feature_flags         :bigint           default(0), not null
+#  internal_attributes   :jsonb            not null
+#  limits                :jsonb
+#  locale                :integer          default("en")
+#  name                  :string           not null
+#  status                :integer          default("active")
+#  support_email         :string(100)
+#  created_at            :datetime         not null
+#  updated_at            :datetime         not null
 #
 # Indexes
 #