feat: broadcast worst-case OBC temperature on 0x211 byte 7

The Tesla OBC hardware already publishes 9 temperature probes (3
modules × {tmp1, tmp2, tmpin}) on CAN 0x237/0x239/0x23B which the
teslacharger receives as c[123]tmp[12,in]. Until now none of these
were forwarded downstream — the Polarity VCU's STATUS_SCREEN OBC-temp
and DCDC-temp fields rendered 0 °C on OI-OBC cars.

This commit:

- Adds Param::tmpobcmax — derived value computed each Ms100Task tick
  as the max across the 9 probes, skipping any that read -40 °C
  (sensor absent / module not present).
- Maps it to 0x211 byte 7 (previously reserved, the last unused byte
  of the 7-byte frame). Wire encoding uses the Tesla OBC convention
  of offset 40 (wire = °C + 40), matching c[123]tmp* upstream so
  receivers can decode with the same formula.
- Bumps VERSTR to -S5 so the right firmware is visually confirmable
  in the OpenInverter web UI.

The new byte is purely additive — existing 0x211 consumers that read
only bytes 0-6 continue to work unchanged.

The Polarity VCU's 0x211 RX handler grows a corresponding decode +
display path in a paired stm32-hal-vcu commit.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

include/param_prj.h

@@ -47,7 +47,7 @@
    3. Display values
  */
 //Next param id (increase when adding new parameter!): 24
-//Next value Id: 2051
+//Next value Id: 2052
 /*              category     name         unit       min     max     default id */
 #define PARAM_LIST \
     PARAM_ENTRY(CAT_CHARGER, idclim,      "A",       0,      45,     45,     3   ) \
@@ -108,6 +108,7 @@
     VALUE_ENTRY(c3iac,       "A",     2034 ) \
     VALUE_ENTRY(c3udc,       "V",     2035 ) \
     VALUE_ENTRY(c3idc,       "A",     2036 ) \
+    VALUE_ENTRY(tmpobcmax,   "°C",    2051 ) \
     VALUE_ENTRY(test_time,   "s",     3000 ) \
     VALUE_ENTRY(test_timer_flag,   "X",     3001 ) \
     VALUE_ENTRY(test_timer_icvalue,   "X",     3002 ) \
@@ -128,7 +129,7 @@
 // SKUDAK customization suffix: bump on every Skudak-side change so the OpenInverter
 // web UI shows a distinct version (e.g. "4=1.20.R-S4") and we can visually confirm
 // the right firmware is flashed. Match the stm32-sine -S<N> convention.
-#define VERSTR STRINGIFY(4=VER-S4)
+#define VERSTR STRINGIFY(4=VER-S5)
 
 /***** enums ******/