refactor: replace hr separators with light well containers in TransactionDetail

Replace horizontal rules (<hr>) between TransactionDetail groups with
bg-well container divs matching the Settings view pattern. Each logical
group (Identity, Timing, Value, Decoded Details, Network Details, Raw
Data) is now wrapped in a bg-well p-3 mx-1 mb-3 container with an h3
heading, providing subtle background-based visual grouping instead of
line separators.

Conditional groups (Decoded, Network, Raw Data) retain their visibility
toggling with the bg-well wrapper inside the hidden container.

Update README TransactionDetail section to reflect light well containers.

Closes #131

README.md

@@ -435,7 +435,8 @@ transitions.
 #### TransactionDetail
 
 - **When**: User tapped a transaction row from AddressDetail or AddressToken.
-- **Elements** (grouped into logical blocks separated by thin rules):
+- **Elements** (grouped into logical blocks using light well containers,
+  matching the Settings view pattern):
     - "Transaction" heading, "Back" button
     - **Identity block**:
         - Transaction hash: full hash (tap to copy) + etherscan link