feat: remove balance-bot safety constraints from ESP32 Balance firmware

Platform is no longer a self-balancing bot. Remove:
- TILT_CUTOFF_DEG (±25° tilt cutoff constant, was unused in ESP32-S3)
- BAL_TILT_FAULT state from bal_state_t enum (no code path generates it)

ESTOP and heartbeat watchdog are unchanged.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

esp32s3/balance/main/config.h

@@ -38,5 +38,3 @@
 #define RPM_PER_SPEED_UNIT      5       /* speed_units=1000 → 5000 ERPM */
 #define RPM_PER_STEER_UNIT      3       /* steer differential scale */
 
-/* ── Tilt cutoff ── */
-#define TILT_CUTOFF_DEG         25.0f

esp32s3/balance/main/orin_serial.h

@@ -53,10 +53,9 @@
 
 /* ── Balance state (mirrored from TELEM_STATUS.balance_state) ── */
 typedef enum {
-    BAL_DISARMED   = 0,
-    BAL_ARMED      = 1,
-    BAL_TILT_FAULT = 2,
-    BAL_ESTOP      = 3,
+    BAL_DISARMED = 0,
+    BAL_ARMED    = 1,
+    BAL_ESTOP    = 3,
 } bal_state_t;
 
 /* ── Shared state written by RX task, consumed by main/vesc tasks ── */