Add collector performance diagnostics to Lite UI

[erikdarlingdata]

Problem

Every collector in Lite tracks split timing via Stopwatch — SQL Server query time (sql_duration_ms) and DuckDB insert time (duckdb_duration_ms) — and logs both to the collection_log table and to disk (logs/lite_YYYYMMDD.log). But none of this timing data is surfaced in the UI.

When a collector starts timing out (like the XE ring buffer issue in #37), the only way to diagnose it today is to:

• Read the log file manually from logs/ on disk
• Query the collection_log DuckDB table directly
• Use the MCP get_collection_health tool

There's no way for a user to see that a collector is getting slower over time, or whether the bottleneck is SQL Server or DuckDB.

Proposed Solution

Add a diagnostics view (tab, panel, or window) that shows:

1. Collector timing grid — recent collection_log entries showing collector name, duration, SQL vs DuckDB split, rows collected, status
2. Timing trend chart — per-collector duration over time to spot degradation
3. Log viewer — display recent entries from the daily log file, or at minimum an "Open Log File" button

The collection_log table already has all the data needed:

• collector_name, collection_time, duration_ms, sql_duration_ms, duckdb_duration_ms
• rows_collected, status, error_message

Related Files

• Lite/Database/Schema.cs — collection_log table schema (line 37), split timing columns added in v4 migration
• Lite/Services/RemoteCollectorService.cs — _lastSqlMs / _lastDuckDbMs fields (line 89), LogCollectionAsync() (line 372)
• Lite/Services/LocalDataService.CollectionHealth.cs — GetCollectionHealthAsync() query (line 21)
• Lite/Services/AppLogger.cs — file-based logging implementation

[erikdarlingdata]

Implemented in PR #43.