Work through the remaining review items in TODO.md

Keep the HTTP session alive between weather polls (TODO #1). Re-creating the
client each time forced a fresh TLS handshake inside the window where the UI
is frozen. Measured on hardware: the fetch went from ~1.3s to ~80ms, so the
pause is no longer long enough to matter once thermostat controls exist. The
timeout drops from 30s to 10s once a session is warm, since only a cold
handshake needs the longer budget. Any transport error or non-200 tears the
session down so a half-open connection cannot poison every later poll.

The response buffer is now reset per request rather than on
HTTP_EVENT_ON_CONNECTED -- a kept-alive connection does not re-fire that
event, so the buffer would have accumulated across polls.

Indicate stale readings (TODO #2). After two consecutive failures the
temperature dims and the status line shows the age. Age comes from tick
counts, not weather_data_t.last_update: there is no SNTP client here, so
time(NULL) starts at the epoch and any age derived from it is meaningless.

Gate the touch readout behind UI_DEBUG_TOUCH, default off (TODO #3). Kept the
note about LVGL not bubbling events to parents -- it documents a real trap.

Delete main/utils (TODO #4); it had no callers outside itself. Also refreshed
project_structure.txt, which was additionally missing i2c_bus and backlight.

Lay out two 4MB OTA slots (TODO #5) while no devices are fielded, and document
in the README that an OTA download cannot run while the panel is scanning --
the flash write faults the bounce-buffer ISR.

Log the truncation warning once per response instead of once per chunk, and
record the weather task's stack high-water mark (TODO #6): ~2400 bytes spare
of 6144.

Co-Authored-By: Claude <noreply@anthropic.com>

partitions.csv

@@ -1,8 +1,24 @@
 # Partition table for ESP32-S3-WROOM-1-N16R8 (16MB flash, 8MB octal PSRAM)
 # as fitted to the CrowPanel 7" Advance.
 #
+# Two 4MB OTA slots. The app is ~1.1MB, so this is generous -- but the layout
+# is fixed once devices are in the field, and re-partitioning later means
+# reflashing each one over USB. Laying the slots out now costs nothing.
+#
+# NOTE: writing an OTA image is a flash write, and the panel's bounce-buffer
+# refill ISR reads PSRAM, which shares the cache with flash on the S3. An OTA
+# download while the panel is scanning WILL fault that ISR ("Cache disabled but
+# cached memory region accessed"). Any OTA implementation must stop the panel
+# for the download+write, or reboot into a dedicated updater mode first. See
+# README "Memory notes".
+#
+# The former 12MB SPIFFS partition was dropped -- nothing mounted it. ~7.9MB
+# is left unallocated for a filesystem or a third slot if either is ever
+# needed; adding a partition to free space is safe, moving one is not.
+#
 # Name,     Type, SubType,  Offset,   Size,      Flags
 nvs,        data, nvs,      0x9000,   0x6000,
-phy_init,   data, phy,      0xf000,   0x1000,
-factory,    app,  factory,  0x10000,  0x400000,
-storage,    data, spiffs,   0x410000, 0xBF0000,
+otadata,    data, ota,      0xf000,   0x2000,
+phy_init,   data, phy,      0x11000,  0x1000,
+ota_0,      app,  ota_0,    0x20000,  0x400000,
+ota_1,      app,  ota_1,    0x420000, 0x400000,