invoices: payout addresses in the database

Default crypto payout addresses lived in the CRYPTO_ADDRESSES and
LTC_ADDRESS Forgejo secrets, so changing one meant editing a secret and
redeploying. Keep them in a payout_addresses table edited at
/admin/invoices/payout-addresses (read to view, write to change, every
change audited), and prefill the new-invoice form from it.

The old env values are imported once on the first boot with an empty
table, so the current addresses carry over; after that the secrets can
be removed.

Assisted-by: Claude:opus-5

lib/payout_address.rb

@@ -0,0 +1,36 @@
+require 'sequel'
+require_relative 'crypto_asset'
+
+# Default payout address per coin (see migration 010).
+class PayoutAddress < Sequel::Model(:payout_addresses)
+  unrestrict_primary_key
+  ADDRESS_RE = /\A[a-zA-Z0-9]{10,128}\z/ # same loose shape check as invoices
+
+  def self.map
+    to_hash(:coin, :address).slice(*CryptoAsset::CODES)
+  end
+
+  # First boot after the move: take over what the env/Forgejo secrets held.
+  def self.seed_from_env!
+    return if count.positive?
+    CryptoAsset.env_addresses.each do |coin, address|
+      next unless address.match?(ADDRESS_RE)
+      create(coin: coin, address: address, updated_by: 'env import', updated_at: Time.now.utc)
+    end
+  end
+
+  # Upsert or (blank address) delete. Returns an error string or nil.
+  def self.set!(coin, address, by:)
+    coin = coin.to_s.upcase
+    return 'unknown coin' unless CryptoAsset.valid?(coin)
+    address = address.to_s.strip
+    if address.empty?
+      where(coin: coin).delete
+      return nil
+    end
+    return "#{coin}: address looks invalid" unless address.match?(ADDRESS_RE)
+    row = self[coin] || new(coin: coin)
+    row.set(address: address, updated_by: by, updated_at: Time.now.utc).save
+    nil
+  end
+end