sp_BlitzBackups: use @starttime for CheckId 7 and 12

The "No CHECKSUMS" (CheckId 7) and "Uncompressed backups" (CheckId 12)
checks were filtering on a hard-coded 30-day window via
DATEADD(DAY, -30, SYSDATETIME()) instead of the user-supplied
@HoursBack window already exposed via @starttime. That ignored
@HoursBack and made the warning text inconsistent with the actual
window being analyzed.

Replace both filters with @starttime, pass @starttime through
sp_executesql, and drop the "in the last 30 days" / "in the past 30
days" wording from the findings now that the window is dynamic. Same
treatment as PR BrentOzarULTD#3960 applied to CheckId 14.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: BrentOzar

sp_BlitzBackups.sql

@@ -975,18 +975,18 @@ RAISERROR('Rules analysis starting', 0, 1) WITH NOWAIT;
 								100 AS [Priority],
 								b.database_name AS [Database Name],
 								''No CHECKSUMS'' AS [Finding],
-								''The database '' + QUOTENAME(b.database_name) + '' has been backed up '' + CONVERT(VARCHAR(10), COUNT(*)) + '' times without CHECKSUMS in the past 30 days. CHECKSUMS can help alert you to corruption errors.'' AS [Warning]
+								''The database '' + QUOTENAME(b.database_name) + '' has been backed up '' + CONVERT(VARCHAR(10), COUNT(*)) + '' times without CHECKSUMS. CHECKSUMS can help alert you to corruption errors.'' AS [Warning]
 							FROM   ' + QUOTENAME(@MSDBName) + N'.dbo.backupset AS b
 							WHERE b.has_backup_checksums = 0
-							AND b.backup_finish_date >= DATEADD(DAY, -30, SYSDATETIME())
+							AND b.backup_finish_date >= @StartTime
 							GROUP BY b.database_name;' + @crlf;
 
 	IF @Debug = 1
 		PRINT @StringToExecute;
 
 		INSERT #Warnings ( CheckId, Priority, DatabaseName, Finding, Warning )
-		EXEC sys.sp_executesql @StringToExecute;
-	
+		EXEC sys.sp_executesql @StringToExecute, N'@StartTime DATETIME2', @StartTime;
+
 	/*Damaged is a Black Flag album. You don''t want your backups to be like a Black Flag album. */
 
 	SET @StringToExecute = N'SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;' + @crlf;
@@ -1089,17 +1089,17 @@ IF @ProductVersionMajor >= 12
 		100 AS [Priority],
 		b.database_name AS [Database Name],
 		''Uncompressed backups'' AS [Finding],
-		''The database '' + QUOTENAME(b.database_name) + '' has had '' + CONVERT(VARCHAR(10), COUNT(*)) + '' uncompressed backups in the last 30 days. This is a free way to save time and space. And SPACETIME. If your version of SQL supports it.'' AS [Warning]
+		''The database '' + QUOTENAME(b.database_name) + '' has had '' + CONVERT(VARCHAR(10), COUNT(*)) + '' uncompressed backups. This is a free way to save time and space. And SPACETIME. If your version of SQL supports it.'' AS [Warning]
 	FROM   ' + QUOTENAME(@MSDBName) + '.dbo.backupset AS b
 	WHERE backup_size = compressed_backup_size AND type = ''D''
-	AND b.backup_finish_date >= DATEADD(DAY, -30, SYSDATETIME())
+	AND b.backup_finish_date >= @StartTime
 	GROUP BY b.database_name;' + @crlf;
 
 	IF @Debug = 1
 		PRINT @StringToExecute;
 
 		INSERT #Warnings ( CheckId, Priority, DatabaseName, Finding, Warning )
-		EXEC sys.sp_executesql @StringToExecute;
+		EXEC sys.sp_executesql @StringToExecute, N'@StartTime DATETIME2', @StartTime;
 
 	/*Looking for backups directed at the NUL device.*/
 	SET @StringToExecute =N'SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;' + @crlf;