perf(memory): optimize C++ string operations to reduce heap fragmentation

- Replaced pass-by-value std::string parameters with const std::string&
or std::string_view to prevent SSO overallocations.

- Refactored static mapping functions in UPower to return
std::string_view instead of constructing std::string literals, enabling
perfect cache locality.

- Optimized string concatenation in hot loops (network IPs, inhibitor
lists, sway window marks) by using std::string::append() and
pre-reserving capacity instead of overloaded operator+ which produces
temporary heap instances.

These optimizations reduce high-frequency memory churn and overall heap
fragmentation within the main rendering loops.

Signed-off-by: Austin Horstman <khaneliman12@gmail.com>

include/modules/sway/language.hpp

@@ -47,7 +47,7 @@ class Language : public ALabel, public sigc::trackable {
   void onEvent(const struct Ipc::ipc_response&);
   void onCmd(const struct Ipc::ipc_response&);
 
-  auto set_current_layout(std::string current_layout) -> void;
+  auto set_current_layout(const std::string& current_layout) -> void;
   auto init_layouts_map(const std::vector<std::string>& used_layouts) -> void;
 
   const static std::string XKB_LAYOUT_NAMES_KEY;