Rename host library to master throughout

The two libraries are now "master" and "slave" everywhere: UI text, API
JSON fields (master_root, rel_master, master_size, ...), Go identifiers,
database columns, quality verdicts, quarantine subfolders and docs.

Existing databases are upgraded by a new migration that renames the
columns in place and rewrites stored "host" values, so pairs, history,
cached verdicts and restorable quarantine entries carry over. Network
"host" usages (SplitHostPort, the Origin/Host check) are unchanged.

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

internal/store/store.go

@@ -91,6 +91,19 @@ var migrations = []string{
 		purged_at INTEGER
 	);
 	CREATE INDEX operations_pair ON operations(pair_id, created_at DESC);`,
+
+	// 2: the "host" library was renamed to "master". Rename in place so
+	// existing pairs, history and quarantine entries carry over.
+	`ALTER TABLE pairs RENAME COLUMN host_root TO master_root;
+	ALTER TABLE matches RENAME COLUMN rel_host TO rel_master;
+	ALTER TABLE matches RENAME COLUMN host_ino TO master_ino;
+	ALTER TABLE matches RENAME COLUMN host_size TO master_size;
+	ALTER TABLE matches RENAME COLUMN host_mtime TO master_mtime;
+	ALTER TABLE matches RENAME COLUMN host_probe TO master_probe;
+	ALTER TABLE operations RENAME COLUMN rel_host TO rel_master;
+	UPDATE operations SET quarantine_side = 'master' WHERE quarantine_side = 'host';
+	UPDATE matches SET verdict = replace(verdict, 'host', 'master');
+	UPDATE pairs SET last_scan_warnings = replace(last_scan_warnings, 'host', 'master');`,
 }
 
 // Open opens (and migrates) the database in dataDir.