core: name the unique index on wallet_seeds

The one key per device rule is meant to be lifted later. SQLite cannot drop
a column with an inline UNIQUE, or its automatic index, so lifting it would
have meant rebuilding the table. As a named index it is a DROP INDEX and a
DROP COLUMN.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Rvc3HbiWBTqbAvRT45G5oX

src/Simplex/Chat/Store/Postgres/Migrations/M20260908_wallet_seeds.hs

@@ -15,12 +15,13 @@ CREATE TABLE wallet_seeds (
   -- see the SQLite migration
   next_account_index BIGINT NOT NULL DEFAULT 0,
   -- one key per device for now
-  single_seed SMALLINT NOT NULL DEFAULT 1 UNIQUE
+  single_seed SMALLINT NOT NULL DEFAULT 1
 );
 
 ALTER TABLE users ADD COLUMN wallet_seed_id BIGINT REFERENCES wallet_seeds ON DELETE RESTRICT;
 ALTER TABLE users ADD COLUMN wallet_account_index BIGINT;
 
+CREATE UNIQUE INDEX idx_wallet_seeds_single_seed ON wallet_seeds(single_seed);
 CREATE INDEX idx_users_wallet_seed_id ON users(wallet_seed_id);
 |]
 

src/Simplex/Chat/Store/Postgres/Migrations/chat_schema.sql

@@ -1918,11 +1918,6 @@ ALTER TABLE ONLY test_chat_schema.wallet_seeds
 
 
 
-ALTER TABLE ONLY test_chat_schema.wallet_seeds
-    ADD CONSTRAINT wallet_seeds_single_seed_key UNIQUE (single_seed);
-
-
-
 ALTER TABLE ONLY test_chat_schema.xftp_file_descriptions
     ADD CONSTRAINT xftp_file_descriptions_pkey PRIMARY KEY (file_descr_id);
 
@@ -2676,6 +2671,10 @@ CREATE INDEX idx_users_wallet_seed_id ON test_chat_schema.users USING btree (wal
 
 
 
+CREATE UNIQUE INDEX idx_wallet_seeds_single_seed ON test_chat_schema.wallet_seeds USING btree (single_seed);
+
+
+
 CREATE INDEX idx_xftp_file_descriptions_user_id ON test_chat_schema.xftp_file_descriptions USING btree (user_id);