fix: a backup restores text that looks like a number as text

[blaipr]

The database backup dump (BackupFile) wrote every value is_numeric() accepted as a bare SQL literal. is_numeric() is true of text that only looks numeric, and a bare literal is a number to MySQL. So restoring a backup silently changed text columns:

CREATE TEMPORARY TABLE t (v varchar(20));
INSERT INTO t VALUES(0123),(1e5),( 7),(0800),('0123');
SELECT v FROM t;   -- 123, 100000, 7, 800, 0123

So an account login of 0123, an account or client named 0800, or a note reading 1e5 would come back as 123, 800 and 100000. The backup is the recovery path, so this only shows up on the day it's needed.

Change

The decision is now made by the column's type, not by what the value looks like:

• PDO returns integer columns as int and every text column as string. This was measured against MariaDB with both native and emulated prepares.
• Only real ints and floats are written bare. Everything else is quoted.
• A quoted number still loads correctly into a numeric column.

Tests

FileBackupServiceTest::testTextThatLooksLikeANumberIsDumpedAsText checks that a row of '0123', 5, '1e5', ' 7', 2.5, NULL is dumped as VALUES('0123',5,'1e5',' 7',2.5,NULL). It fails without the fix.