Release v1.2.2 with stability improvements and optimizations

This version includes a stability patch to address spontaneous reboots during price fetch. Key updates include increased ESP32 task watchdog timeout, optimized JSON string building, periodic yield calls, and added heap monitoring logs. Added v1.2.2 section with 4-bullet summary of all changes.

VERSION.md

@@ -1,5 +1,44 @@
 # EPrices – Version History
 
+## v1.2.2 — 2026-04-28
+
+Stability patch addressing spontaneous reboots during tomorrow price fetch at ~13:55.
+No new sensors, no secrets changes, no entity ID changes. Drop-in replacement for v1.2.1.
+
+### ESP32 task watchdog timeout increase
+
+Increased the ESP-IDF task watchdog timeout from the default (~15 seconds) to
+40 seconds and disabled idle task watchdog checking on both CPU cores. This
+prevents false-positive watchdog resets during heavy JSON parsing when full price
+data arrives (~13:55 and subsequent retry attempts).
+
+**Root cause:** The first API call at 13:25 typically returns no data
+(Energy-Charts usually hasn't published tomorrow's prices yet), so no heavy
+parsing occurs. By 13:55, complete data is available, triggering the full
+parsing chain that exceeded the default watchdog timeout.
+
+### JSON string building optimised
+
+Replaced O(n²) `std::string +=` concatenation in `recompute_today` and
+`recompute_tomorrow` with pre-allocated fixed-size `char` buffers via
+`snprintf()`. Eliminates heap fragmentation and peak memory spikes during JSON
+building for the 8 JSON text sensors.
+
+### Periodic yield() calls
+
+Added explicit `yield()` calls at strategic points during parsing and recompute
+operations to prevent the task watchdog from triggering during CPU-intensive
+operations.
+
+### Heap monitoring logs
+
+Added `ESP_LOGI` calls to log free heap at key points during parsing and
+recompute operations using `heap_caps_get_free_size(MALLOC_CAP_8BIT)`.
+
+See `CHANGELOG.md` for full implementation details.
+
+---
+
 ## v1.2.1 — 2026-04-07
 
 Stability and housekeeping patch. No new sensors, no secrets changes,