perf(memory): eliminate deep copies in range-based for loops and lambdas

This commit addresses memory churn caused by implicit deep copies during traversal and allocation of complex structures:

- Replaced pass-by-value 'Json::Value' in std::ranges and range-based for loops with 'const auto&' or 'const Json::Value&' in Hyprland modules, preventing large JSON tree duplications on every update.

- Fixed implicit string and pair copies in UPower and CPU Frequency loops by converting 'auto' to 'const auto&' where possible.

- Added 'std::vector::reserve' calls before 'push_back' loops in MPRIS, Niri, and CFFI modules to prevent exponential vector reallocation during initialization.

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

src/modules/cpu_frequency/linux.cpp

@@ -26,7 +26,7 @@ std::vector<float> waybar::modules::CpuFrequency::parseCpuFrequencies() {
     if (std::filesystem::exists(cpufreq_dir)) {
       std::vector<std::string> frequency_files = {"/cpuinfo_min_freq", "/cpuinfo_max_freq"};
       for (auto& p : std::filesystem::directory_iterator(cpufreq_dir)) {
-        for (auto freq_file : frequency_files) {
+        for (const auto& freq_file : frequency_files) {
           std::string freq_file_path = p.path().string() + freq_file;
           if (std::filesystem::exists(freq_file_path)) {
             std::string freq_value;