fix(firmware): provision.py nvs import + partition config template

Fixes #215: provision.py now correctly imports from esp_idf_nvs_partition_gen
package (the pip-installable version) before falling back to legacy import.

Fixes #216: Added sdkconfig.defaults.template with custom partition table
configuration for 8MB flash boards. Copy to sdkconfig.defaults before build:
  cp sdkconfig.defaults.template sdkconfig.defaults

Changes:
- firmware/esp32-csi-node/provision.py: Try esp_idf_nvs_partition_gen first
- scripts/provision.py: Same import fix
- firmware/esp32-csi-node/sdkconfig.defaults.template: 8MB flash config with
  2MB OTA partitions, compiler size optimization, and CSI enabled

Co-Authored-By: claude-flow <ruv@ruv.net>

scripts/provision.py

@@ -80,7 +80,16 @@ def generate_nvs_binary(csv_content, size):
     bin_path = csv_path.replace(".csv", ".bin")
 
     try:
-        # Try the pip-installed version first
+        # Try the pip-installed version first (esp_idf_nvs_partition_gen package)
+        try:
+            from esp_idf_nvs_partition_gen import nvs_partition_gen
+            nvs_partition_gen.generate(csv_path, bin_path, size)
+            with open(bin_path, "rb") as f:
+                return f.read()
+        except ImportError:
+            pass
+
+        # Try legacy import name (older versions)
         try:
             import nvs_partition_gen
             nvs_partition_gen.generate(csv_path, bin_path, size)