feat: reward codes

this is for giving rewards across characters as the did in live.
Tested that the default config works
Tested that all claim codes work
Tested that saving and loading claim codes work
Tested that mail sends correctly

migrations/dlu/14_reward_codes.sql

@@ -0,0 +1,5 @@
+CREATE TABLE IF NOT EXISTS accounts_rewardcodes (
+    account_id INT NOT NULL REFERENCES accounts(id),
+    rewardcode INT NOT NULL,
+    PRIMARY KEY (account_id, rewardcode)
+);