Closes #281 (Gaps 1 and 2)

Summary

• Gap 1 (memory_grant_stats): Add memory grant stats charts to both apps — active grants, queued, memory pressure trend
• Gap 2 (file_io_stats): Add File I/O throughput charts, switch Lite latency to file-level, add queued I/O overlay

Changes

Both apps

• Add "File I/O Throughput" sub-tab with read/write MB/s charts per file (top 10 by bytes)
• Restructure "File I/O" tab into "File I/O Latency" and "File I/O Throughput" sub-tabs
• Add queued I/O overlay (dashed lines) on latency charts showing OS queue wait time

Lite-specific

• Memory grants tab with active grants, queued requests, and memory grant trend charts
• Switch File I/O latency charts from database-level to file-level (top 10 by I/O activity)
• Collect io_stall_queued_read/write_ms from sys.dm_io_virtual_file_stats
• DuckDB schema v15 migration adds queued stall columns to file_io_stats
• Use DuckDB LAG() window function for throughput MB/s interval calculation

Dashboard-specific

• Memory grants trend chart added to Resource Metrics tab
• Fix double-brace interpolation bug in GetFileIoThroughputTimeSeriesAsync that caused empty throughput charts

CI fix

• Update 50_configuration_issues_analyzer.sql and 97_test_procedures.sql to remove references to warning columns dropped from collect.memory_grant_stats in Gap 1

Test plan

• Dashboard: Resource Metrics → File I/O → "File I/O Latency" sub-tab shows per-file latency with queued I/O dashed overlay
• Dashboard: Resource Metrics → File I/O → "File I/O Throughput" sub-tab shows read/write MB/s per file
• Lite: File I/O → "File I/O Latency" sub-tab shows per-file (not per-database) latency with queued overlay
• Lite: File I/O → "File I/O Throughput" sub-tab shows read/write MB/s per file
• CI passes (configuration issues analyzer + test procedures use updated column references)

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