opam package categories, logpath and dates are treated as regular tags

[palmskog]

As per CEP 3, the Coq opam archive has the following special fields under tags:

• logpath that states the Coq logical path prefix, e.g., mathcomp.ssreflect
• category that has a limited number of possible values, e.g., Miscellaneous/Coq Use Examples
• date that has the release date like 2024-12-25

However, all of these are treated like regular tags on the website (which they clearly are not) and we get links like https://rocq-prover.org/packages/search?q=tag%3A%22logpath%3Amathcomp.ssreflect%22

I also think the keyword part should be stripped from tag links, i.e., the keyword entries are our actual tags.