Remove dynamic memory allocation (malloc/calloc/free)

- Add static memory pool implementation (se050_mem_pool.c/h)
- Replace all malloc/calloc with pool allocations
- Replace all free with pool deallocations
- Remove strdup usage (use fixed-size buffer instead)
- Update I2C HAL to use fixed-size dev_path array
- All 24 tests pass with static memory only

Suitable for embedded environments (u-boot, ESP32) without heap.

src/se050_i2c_hal.c

@@ -136,7 +136,8 @@ se050_status_t se050_i2c_init(se050_i2c_hal_t *hal, const char *dev_path, uint8_
     
     hal->handle = handle;
     hal->slave_addr = slave_addr;
-    hal->dev_path = strdup(dev_path);
+    strncpy(hal->dev_path, dev_path, SE050_I2C_DEV_PATH_MAX - 1);
+    hal->dev_path[SE050_I2C_DEV_PATH_MAX - 1] = '\0';
     
     return SE050_OK;
 }
@@ -152,11 +153,7 @@ void se050_i2c_close(se050_i2c_hal_t *hal)
         hal->handle = NULL;
     }
     
-    if (hal->dev_path) {
-        free((void *)hal->dev_path);
-        hal->dev_path = NULL;
-    }
-    
+    hal->dev_path[0] = '\0';
     hal->slave_addr = 0;
 }