chore: rewrite uses of cs.tvl.fyi to code.tvl.fyi

I've checked the new links manually.

- //web/tvl: changed the target path of links to the tvix docs since
  they were moved in r/2378.

- //users/aspen/resume: Tvix is no longer //third_party/nix.

Change-Id: I419bae1a46bdccc7baa7327215aa2368ffc0f01c
Reviewed-on: https://cl.tvl.fyi/c/depot/+/13043
Reviewed-by: aspen <root@gws.fyi>
Tested-by: BuildkiteCI
Autosubmit: sterni <sternenseemann@systemli.org>
Reviewed-by: fogti <fogti+devel@ytrizja.de>
Reviewed-by: tazjin <tazjin@tvl.su>

web/tvixbolt/src/lib.rs

@@ -75,7 +75,7 @@ fn footer() -> Html {
         <footer>
           <p class="footer">
             {footer_link("https://tvl.fyi", "home")}
-            {footer_link("https://cs.tvl.fyi", "code")}
+            {footer_link("https://code.tvl.fyi", "code")}
             {footer_link("https://tvl.fyi/builds", "ci")}
             {footer_link("https://b.tvl.fyi", "bugs")}
             {"© TVL"}