fix(common): harden CORS, sort, raw-SQL WHERE and x-custom-sql-or

Add a `hardening` config section (RESOLVESPEC_HARDENING_*) so each
fix can be switched off to restore the previous behaviour:

- cors_strict_origins: only reflect origins listed in
  cors.allowed_origins / server URLs, with credentials; `*` never
  sends credentials; fix shared-slice append of expose headers.
- sort_strict: join aliases must match `alias.identifier` (empty alias
  no longer matches everything); sort expressions reject dangerous
  functions/catalogs; cql* columns must be identifier-safe.
- sql_strict: client raw-SQL fragments must have balanced parens and
  quotes, no comments/`;`/`$$`, DML keywords, dangerous functions or
  system catalogs; a rejected fragment now fails closed ("(1=0)")
  instead of dropping the filter. Subqueries stay allowed unless
  sql_block_subqueries is set.
- x-custom-sql-or is grouped together with the client's own
  conditions (new optional WhereGrouper, implemented for bun and gorm)
  so it can no longer OR past server-side filters.

pkg/common/interfaces.go

@@ -319,3 +319,11 @@ type QueryHandler interface {
 	SpecHandler
 	// Methods are defined in funcspec package due to different function signature requirements
 }
+
+// WhereGrouper is implemented by query builders that can wrap a set of
+// conditions (including WhereOr) in one parenthesised group that is ANDed with
+// the rest of the query. It is optional so existing SelectQuery implementations
+// keep compiling.
+type WhereGrouper interface {
+	WhereGroup(fn func(SelectQuery) SelectQuery) SelectQuery
+}