Fix numeroContrato: use EMPRESA.CODCONTRATO from Firebird, sucursal default 00

- Join EMPRESA table in all RDA queries to get CODCONTRATO (TNS contract code)
- Use EMPRESA.CODCONTRATO as numeroContrato instead of raw NIT_EMPRESA
- Especialidad always uses default_especialidad (ignore Firebird COD_ESPECIALIDAD)
- sucursal defaults to '00' (not empty) in config and endpoints
- Fix config template label: especialidad default is TNS code not Firebird code

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

app/routes/config.py

@@ -17,7 +17,7 @@ DEFAULT_KEYS = [
     ("api_key", ""),
     ("api_timeout", "30"),
     ("api_version", "1"),
-    ("api_sucursal", ""),
+    ("api_sucursal", "00"),
     ("tns_empresa", "9002787299"),
     ("tns_usuario", "DOCUXER"),
     ("tns_password", "Nicolas2796*+"),