chat: exclude soft-deleted contacts from idx_contacts_simplex_name

The lookup `getContactBySimplexName` (Store/Direct.hs:781) filters
`AND deleted = 0`, but the index predicate `WHERE simplex_name IS NOT
NULL` covered tombstoned rows too. Forward-compat trap: once writers
land a non-Nothing simplex_name, soft-deleting a contact would block
re-claiming its name (UNIQUE conflict) even though the lookup reports
the slot as free.

Tighten the partial-index predicate to also require deleted = 0 so the
constraint scope matches the live-lookup scope. Groups have no soft-
delete column, so their index stays as-is.

src/Simplex/Chat/Store/Postgres/Migrations/M20260603_simplex_name.hs

@@ -15,7 +15,7 @@ ALTER TABLE connections ADD COLUMN simplex_name TEXT;
 
 CREATE UNIQUE INDEX idx_contacts_simplex_name
   ON contacts(user_id, simplex_name)
-  WHERE simplex_name IS NOT NULL;
+  WHERE simplex_name IS NOT NULL AND deleted = 0;
 
 CREATE UNIQUE INDEX idx_groups_simplex_name
   ON groups(user_id, simplex_name)

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

@@ -2193,7 +2193,7 @@ CREATE INDEX idx_contacts_grp_direct_inv_from_member_conn_id ON test_chat_schema
 
 
 
-CREATE UNIQUE INDEX idx_contacts_simplex_name ON test_chat_schema.contacts USING btree (user_id, simplex_name) WHERE (simplex_name IS NOT NULL);
+CREATE UNIQUE INDEX idx_contacts_simplex_name ON test_chat_schema.contacts USING btree (user_id, simplex_name) WHERE ((simplex_name IS NOT NULL) AND (deleted = 0));
 
 
 

src/Simplex/Chat/Store/SQLite/Migrations/M20260603_simplex_name.hs

@@ -14,7 +14,7 @@ ALTER TABLE connections ADD COLUMN simplex_name TEXT;
 
 CREATE UNIQUE INDEX idx_contacts_simplex_name
   ON contacts(user_id, simplex_name)
-  WHERE simplex_name IS NOT NULL;
+  WHERE simplex_name IS NOT NULL AND deleted = 0;
 
 CREATE UNIQUE INDEX idx_groups_simplex_name
   ON groups(user_id, simplex_name)

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

@@ -1315,7 +1315,7 @@ ON contacts(
   user_id,
   simplex_name
 )
-WHERE simplex_name IS NOT NULL;
+WHERE simplex_name IS NOT NULL AND deleted = 0;
 CREATE UNIQUE INDEX idx_groups_simplex_name
 ON groups(
   user_id,