Fix database collation for utf8mb4_unicode_ci columns

[projectedanx]

The previous implementation converted all columns to utf8mb4_bin, which wiped the required utf8mb4_unicode_ci collations on columns like title and ip. This fix updates yourls_upgrade_505_to_506 and yourls_upgrade_to_506 to restore utf8mb4_unicode_ci for the title and ip columns exactly after applying the global utf8mb4_bin conversion, effectively targeting keyword and url.

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PR created automatically by Jules for task 3193185667911188223 started by @projectedanx

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[github-actions]

Dependency Review

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[gemini-code-assist]

Code Review

This pull request updates the database upgrade queries in includes/functions-upgrade.php for version 5.0.6, converting the URL table to utf8mb4_bin and adjusting the collations of the title and ip columns. A critical issue was identified where removing the explicit column change for keyword in the upgrade path from older versions prevents reducing its length from VARCHAR(200) to VARCHAR(100). This can trigger index key length limit errors on certain MySQL/MariaDB configurations and cause schema inconsistency. It is recommended to restore the explicit change clause for the keyword column as suggested.

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[gemini-code-assist]

By removing the explicit CHANGE clause for the keyword column, this upgrade path will fail to reduce the keyword column length from VARCHAR(200) to VARCHAR(100) when upgrading from versions prior to 505.

In MySQL/MariaDB, a VARCHAR(200) column using utf8mb4 as a primary key exceeds the default 767-byte index key length limit (200 * 4 = 800 bytes). This will cause the upgrade to fail with a Specified key was too long; max key length is 767 bytes error on standard/older database configurations. Additionally, it leads to schema inconsistency between new installations (which use VARCHAR(100)) and upgraded installations.

We should restore the explicit CHANGE clause for keyword to safely reduce its length to 100 during the table conversion.

            "CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_bin, " .
            "CHANGE `keyword` `keyword` VARCHAR(100) CHARACTER SET utf8mb4 COLLATE utf8mb4_bin NOT NULL DEFAULT '', " .
            "CHANGE `title` `title` TEXT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci, " .
            "CHANGE `ip` `ip` VARCHAR(41) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NOT NULL;"