feat(wallet): migrate legacy points and tokens into the wallet

Adds cmd/wallet-migrate (make wallet-migrate, args=-dry-run to only report),
which moves customer_points and customer_tokens into the wallet
(docs/prd-point-coin.md §10, PC-105). Each customer gets a MIGRATION ledger
row and a non-expiring lot per currency, written through WalletProcessor in
one transaction per customer. EnakCoin is the sum of every token type (Q6),
with the legacy rows listed in the row's metadata.

It credits the difference between the legacy balance and what earlier runs
migrated, so running it again never doubles a balance and picks up only
what the old code added since. A legacy balance that shrank after being
migrated is reported and left alone, since only an admin adjustment may
take balance away, and the command then exits non-zero. It ends with a
legacy / migrated / wallet total per currency.

Migration 000092 renames TOKENS to COINS in campaigns.type and
campaign_rules.reward_type. The campaign API now validates COINS; it still
accepts TOKENS, including as a list filter, and stores it as COINS so older
dashboards keep working while they are updated.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

migrations/000092_rename_campaign_tokens_to_coins.down.sql

@@ -0,0 +1,5 @@
+UPDATE campaigns SET type = 'TOKENS' WHERE type = 'COINS';
+UPDATE campaign_rules SET reward_type = 'TOKENS' WHERE reward_type = 'COINS';
+
+COMMENT ON COLUMN campaigns.type IS 'Type of campaign: REWARD, POINTS, TOKENS, MIXED';
+COMMENT ON COLUMN campaign_rules.reward_type IS 'Type of reward: POINTS, TOKENS, REWARD';