feat: theme constant googleSiteVerification for the Google site verification

The verification code of alvac and cllt came from EXT:metaseo, which is not
installed in TYPO3 13, so their google-site-verification meta tag was
missing. The theme renders the new constant as
page.meta.google-site-verification; empty, it renders no tag. Sites whose
own setup sets the tag (ep-reisen, ski-boarderweek, snowbreak, snowzone, ser)
keep their value.

.ddev/plans/sql/2026-10-25-metaseo-sourceopt.sql renames the metaseo
constants to the new one after the deploy, removes the remaining metaseo
and sourceopt leftovers from the sys_template records, and sets the core
no_index/no_follow flags on the booking links (page 634 and subpages),
which metaseo had kept out of search engines.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

packages/ep_theme/Configuration/TypoScript/Page/Main.typoscript

@@ -4,6 +4,7 @@ page {
         viewport = width=device-width, initial-scale=1
         X-UA-Compatible = ie=edge
         format-detection = telephone=no
+        google-site-verification = {$plugin.tx_eptheme.settings.googleSiteVerification}
     }
 
     bodyTagCObject = COA