feat(logging-p0): add structured logging to database driver services

Add createLogger/trackDuration logging to mysql.ts, sql-server.ts, and
data-source.ts — the only database layer files without observability.
Connect/disconnect, query execution (with duration tracking), and
transaction lifecycle events are now logged. Passwords and parameter
values are excluded; SQL statements are capped at 100 chars.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/main/services/database/mysql.ts

@@ -5,6 +5,9 @@ import type {
   QueryResult,
   MySqlConfig
 } from '../../types/database.types'
+import { createLogger, trackDuration } from '../logger'
+
+const log = createLogger('MySqlService')
 
 export type { MySqlConfig } from '../../types/database.types'
 
@@ -24,6 +27,7 @@ export class MySqlService implements IDatabaseService {
    */
   async connect(): Promise<void> {
     if (this.connection) {
+      log.warn('Already connected to MySQL')
       throw new Error('Already connected to MySQL')
     }
 
@@ -38,7 +42,18 @@ export class MySqlService implements IDatabaseService {
 
       // Test connection
       await this.connection.ping()
+      log.info('Connected to MySQL', {
+        host: this.config.host,
+        port: this.config.port,
+        database: this.config.database
+      })
     } catch (error) {
+      log.error('Failed to connect to MySQL', {
+        host: this.config.host,
+        port: this.config.port,
+        database: this.config.database,
+        error
+      })
       throw new Error(`Failed to connect to MySQL: ${(error as Error).message}`)
     }
   }
@@ -54,7 +69,9 @@ export class MySqlService implements IDatabaseService {
     try {
       await this.connection.end()
       this.connection = null
+      log.info('Disconnected from MySQL')
     } catch (error) {
+      log.error('Failed to disconnect from MySQL', { error })
       throw new Error(`Failed to disconnect from MySQL: ${(error as Error).message}`)
     }
   }
@@ -74,32 +91,40 @@ export class MySqlService implements IDatabaseService {
       throw new Error('Not connected to MySQL. Call connect() first.')
     }
 
+    const sqlPreview = sql.substring(0, 100)
+    const paramCount = params?.length ?? 0
+
     try {
-      const [result, fields] = await this.connection.execute(sql, params)
+      const { result: queryResult } = await trackDuration(
+        async () => {
+          const [result, fields] = await this.connection!.execute(sql, params)
 
-      // Convert to plain objects and extract column names
-      const columns = Array.isArray(fields) ? fields.map((field) => field.name) : []
+          // Convert to plain objects and extract column names
+          const columns = Array.isArray(fields) ? fields.map((field) => field.name) : []
 
-      // Handle different result types
-      let rows: Record<string, unknown>[] = []
-      let rowCount = 0
+          // Handle different result types
+          let rows: Record<string, unknown>[] = []
+          let rowCount = 0
 
-      if (Array.isArray(result)) {
-        // SELECT query - result is an array of rows
-        rows = result as Record<string, unknown>[]
-        rowCount = rows.length
-      } else if (typeof result === 'object' && result !== null) {
-        // INSERT/UPDATE/DELETE query - result is OkPacket
-        const okPacket = result as any
-        rowCount = okPacket.affectedRows || okPacket.changedRows || 0
-      }
+          if (Array.isArray(result)) {
+            // SELECT query - result is an array of rows
+            rows = result as Record<string, unknown>[]
+            rowCount = rows.length
+          } else if (typeof result === 'object' && result !== null) {
+            // INSERT/UPDATE/DELETE query - result is OkPacket
+            const okPacket = result as any
+            rowCount = okPacket.affectedRows || okPacket.changedRows || 0
+          }
 
-      return {
-        rows,
-        columns,
-        rowCount
-      }
+          return { rows, columns, rowCount }
+        },
+        { operationName: 'MySqlService.query' }
+      )
+
+      log.debug('Query executed', { sqlPreview, rowCount: queryResult.rowCount, paramCount })
+      return queryResult
     } catch (error) {
+      log.error('MySQL query failed', { sqlPreview, paramCount, error })
       throw new Error(`MySQL query failed: ${(error as Error).message}`)
     }
   }
@@ -112,17 +137,24 @@ export class MySqlService implements IDatabaseService {
       throw new Error('Not connected to MySQL. Call connect() first.')
     }
 
+    const queryCount = queries.length
+    log.info('Transaction started', { queryCount })
+
     try {
       await this.connection.beginTransaction()
 
-      for (const { sql, params } of queries) {
+      for (let i = 0; i < queries.length; i++) {
+        const { sql, params } = queries[i]
         await this.connection.execute(sql, params)
+        log.debug('Transaction query executed', { index: i, sqlPreview: sql.substring(0, 100) })
       }
 
       await this.connection.commit()
+      log.info('Transaction committed', { queryCount })
     } catch (error) {
       if (this.connection) {
         await this.connection.rollback()
+        log.warn('Transaction rolled back', { queryCount, error })
       }
       throw new Error(`MySQL transaction failed: ${(error as Error).message}`)
     }