feat: add transaction hash search to blockchain explorer and cleanup settlement storage

Blockchain Explorer:
- Add transaction hash search support (64-char hex pattern validation)
- Fetch and display transaction details in modal (hash, type, from/to, amount, fee, block)
- Fix regex escape sequence in block height validation
- Update search placeholder text to mention both search types
- Add blank lines between function definitions for PEP 8 compliance

Settlement Storage:
- Add timedelta import for future

pytest.ini

@@ -1,4 +1,4 @@
-[tool:pytest]
+[pytest]
 # pytest configuration for AITBC
 
 # Test discovery
@@ -12,6 +12,9 @@ markers =
     integration: Integration tests (may require external services)
     slow: Slow running tests
 
+# Test paths to run
+testpaths = tests/cli apps/coordinator-api/tests/test_billing.py
+
 # Additional options for local testing
 addopts = 
     --verbose
@@ -28,6 +31,11 @@ pythonpath =
     apps/wallet-daemon/src
     apps/blockchain-node/src
 
+# Environment variables for tests
+env =
+    AUDIT_LOG_DIR=/tmp/aitbc-audit
+    DATABASE_URL=sqlite:///./test_coordinator.db
+
 # Warnings
 filterwarnings =
     ignore::UserWarning
@@ -35,3 +43,4 @@ filterwarnings =
     ignore::PendingDeprecationWarning
     ignore::pytest.PytestUnknownMarkWarning
     ignore::pydantic.PydanticDeprecatedSince20
+    ignore::sqlalchemy.exc.SADeprecationWarning