Add ICF/SICF management tools (list / get / create / activate / delete / logon data) - #19

What

Adds 7 MCP tools for managing ICF (SICF) service nodes directly from the MCP client, without GUI access to transaction SICF:

How

• Uses standard FMs of function group HTTPTREE (HTTPTREE_INSERT_NODE, HTTPTREE_DELETE_NODE) and HTTP_ACTIVATE_NODE / HTTP_INACTIVATE_NODE (the same APIs behind SAP's own mass-processing report RS_ICF_SERV_MASS_PROCESSING).
• Read tools query ICF data through the ADT data-preview freestyle interface.
• New handlers follow the existing pattern (lib/utils helpers + getConfig + requestSignal); no new npm dependencies.
• Tool annotations: read-only for the 3 read tools, write for the rest, destructiveHint on delete. A known SAP-standard-code limitation of headless HTTPTREE_DELETE_NODE (GUI lock-order dialog) is documented in the tool description with the SICF GUI workaround.

Testing

• npm run build passes; stdio tools/list shows the 7 new tools alongside the existing 16.
• Exercised end-to-end on a real SAP system (ECC6 EHP7 / NW 7.40 SP08): create test node → activate → set logon data → get node → list nodes → deactivate → delete.