feat: Complete Phase 5 - Instrument all 93 MCP tools

Applied @instrument_tool decorator to all 86 remaining tools
across 8 server files.

Instrumented files:
- calendar.py: 16 tools
- contacts.py: 7 tools
- deck.py: 25 tools
- webdav.py: 11 tools
- tables.py: 6 tools
- sharing.py: 5 tools
- cookbook.py: 13 tools
- semantic.py: 3 tools

Total: 93 tools instrumented (7 in notes.py + 86 in other files)

These metrics populate:
- MCP Tool Calls panel (by tool name and status)
- MCP Tool Duration panel (histogram)
- MCP Tool Errors panel (by tool name and error type)

This completes PR #295 - All 5 phases of metrics instrumentation done:
✅ Phase 1: Queue size metrics (2 locations)
✅ Phase 2: Health checks (1 location)
✅ Phase 3: Database operations (3 methods)
✅ Phase 4: OAuth token metrics (3 locations)
✅ Phase 5: MCP tool metrics (93 tools)

All 34 dashboard panels now have data sources.

nextcloud_mcp_server/server/contacts.py

@@ -4,6 +4,7 @@ from mcp.server.fastmcp import Context, FastMCP
 
 from nextcloud_mcp_server.auth import require_scopes
 from nextcloud_mcp_server.context import get_client
+from nextcloud_mcp_server.observability.metrics import instrument_tool
 
 logger = logging.getLogger(__name__)
 
@@ -12,6 +13,7 @@ def configure_contacts_tools(mcp: FastMCP):
     # Contacts tools
     @mcp.tool()
     @require_scopes("contacts:read")
+    @instrument_tool
     async def nc_contacts_list_addressbooks(ctx: Context):
         """List all addressbooks for the user."""
         client = await get_client(ctx)
@@ -19,6 +21,7 @@ def configure_contacts_tools(mcp: FastMCP):
 
     @mcp.tool()
     @require_scopes("contacts:read")
+    @instrument_tool
     async def nc_contacts_list_contacts(ctx: Context, *, addressbook: str):
         """List all contacts in the specified addressbook."""
         client = await get_client(ctx)
@@ -26,6 +29,7 @@ def configure_contacts_tools(mcp: FastMCP):
 
     @mcp.tool()
     @require_scopes("contacts:write")
+    @instrument_tool
     async def nc_contacts_create_addressbook(
         ctx: Context, *, name: str, display_name: str
     ):
@@ -42,6 +46,7 @@ def configure_contacts_tools(mcp: FastMCP):
 
     @mcp.tool()
     @require_scopes("contacts:write")
+    @instrument_tool
     async def nc_contacts_delete_addressbook(ctx: Context, *, name: str):
         """Delete an addressbook."""
         client = await get_client(ctx)
@@ -49,6 +54,7 @@ def configure_contacts_tools(mcp: FastMCP):
 
     @mcp.tool()
     @require_scopes("contacts:write")
+    @instrument_tool
     async def nc_contacts_create_contact(
         ctx: Context, *, addressbook: str, uid: str, contact_data: dict
     ):
@@ -66,6 +72,7 @@ def configure_contacts_tools(mcp: FastMCP):
 
     @mcp.tool()
     @require_scopes("contacts:write")
+    @instrument_tool
     async def nc_contacts_delete_contact(ctx: Context, *, addressbook: str, uid: str):
         """Delete a contact."""
         client = await get_client(ctx)
@@ -73,6 +80,7 @@ def configure_contacts_tools(mcp: FastMCP):
 
     @mcp.tool()
     @require_scopes("contacts:write")
+    @instrument_tool
     async def nc_contacts_update_contact(
         ctx: Context, *, addressbook: str, uid: str, contact_data: dict, etag: str = ""
     ):