chore: strip remaining pre-fork version references

Second pass — removes chat-switchboard version numbers from config
field docs, section headers, file headers, and test comments. These
were pre-fork version tags that don't apply to switchboard-core.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/database/migrate.go

@@ -19,7 +19,7 @@ func SchemaVersion() string { return schemaVersion }
 // Migrate runs all pending migrations for the current dialect.
 // Migration files live in migrations/<dialect>/ subdirectories.
 // Falls back to the root migrations/ directory if no subdirectory exists
-// (backward compatible with pre-v0.17.1 postgres-only layouts).
+// (backward compatible with postgres-only layouts).
 func Migrate() error {
 	if DB == nil {
 		return fmt.Errorf("database not connected")