implement support for pinning

migrations/20250210231615_add_pinned.sql

@@ -0,0 +1,9 @@
+-- Add migration script here
+CREATE TABLE pinned_fish (
+    id SERIAL PRIMARY KEY,
+    account_id VARCHAR(10) NOT NULL,
+    fish_id INTEGER NOT NULL,
+    FOREIGN KEY (account_id) REFERENCES accounts (account_id) ON DELETE CASCADE ON UPDATE NO ACTION
+);
+
+CREATE INDEX pinned_fish_accounts ON pinned_fish (account_id);