Use SPIRAM heap_caps APIs for PSRAM reporting and handle absent PSRAM

[sensenmann]

Motivation

• Ensure PSRAM memory reporting uses the ESP-IDF SPIRAM-aware heap APIs and reports accurate values.
• Provide a clear placeholder when PSRAM is not available instead of producing misleading numbers.
• Keep the displayed label consistent as PSRAM in both inline and detailed free-memory outputs.

Description

• In src/EZLog.cpp update _addFreeMemToMessage() to detect PSRAM with heap_caps_get_total_size(MALLOC_CAP_SPIRAM) and read free size via heap_caps_get_free_size(MALLOC_CAP_SPIRAM).
• In _freeMem() switch PSRAM calculations to use heap_caps_get_free_size and heap_caps_get_largest_free_block for MALLOC_CAP_SPIRAM and conditionally format output based on availability.
• Display PSRAM n/a when no PSRAM is present and keep the PSRAM label consistent in the inline memory summary.
• When PSRAM is absent, set lastMemoryUsagePSRam to zero to avoid spurious delta values.

Testing

• No automated tests were run.

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Codex Task