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/semantic.py

@@ -21,7 +21,10 @@ from nextcloud_mcp_server.models.semantic import (
     SemanticSearchResult,
     VectorSyncStatusResponse,
 )
-from nextcloud_mcp_server.observability.metrics import record_qdrant_operation
+from nextcloud_mcp_server.observability.metrics import (
+    instrument_tool,
+    record_qdrant_operation,
+)
 
 logger = logging.getLogger(__name__)
 
@@ -31,6 +34,7 @@ def configure_semantic_tools(mcp: FastMCP):
 
     @mcp.tool()
     @require_scopes("semantic:read")
+    @instrument_tool
     async def nc_semantic_search(
         query: str, ctx: Context, limit: int = 10, score_threshold: float = 0.7
     ) -> SemanticSearchResponse:
@@ -216,6 +220,7 @@ def configure_semantic_tools(mcp: FastMCP):
 
     @mcp.tool()
     @require_scopes("semantic:read")
+    @instrument_tool
     async def nc_semantic_search_answer(
         query: str,
         ctx: Context,
@@ -544,6 +549,7 @@ def configure_semantic_tools(mcp: FastMCP):
 
     @mcp.tool()
     @require_scopes("semantic:read")
+    @instrument_tool
     async def nc_get_vector_sync_status(ctx: Context) -> VectorSyncStatusResponse:
         """Get the current vector sync status.