GroupVerify: Verification page, overrides and public Verified tags

Shown only where GroupVerify is: staff get the Verification page once its gv_* tables are in
the database, and the public site shows "Verified" only while it's on (enabled, with a group)
and not missing from css_plugins list, which the poller reads once a minute over RCON.

- Verification page: plugin state and version, Steam group, saved member list, overrides.
- Overrides (@zio/verify, not on yourself unless Root): give, change, remove; player drawer
  shows why a player is or isn't verified.
- Root sets the group and turns it on/off: saved to gv_settings, and sent as css_gv_* when the
  plugin is loaded so it applies at once.
- gv_* times use GroupVerify's own timezone setting.
- MySQL integration test (SAW_TEST_DSN), unit tests for plugin list parsing and the show rule.

internal/web/auth.go

@@ -181,7 +181,9 @@ type meView struct {
 	Rank     *rankView `json:"rank,omitempty"`
 	Perms    []string  `json:"perms,omitempty"`
 	Immunity int       `json:"immunity,omitempty"`
-	Site     string    `json:"site"`
+	// Verify is true when GroupVerify's tables are in the database, for the Verification page.
+	Verify bool   `json:"verify,omitempty"`
+	Site   string `json:"site"`
 }
 
 func (s *Server) me(w http.ResponseWriter, r *http.Request) {
@@ -197,6 +199,10 @@ func (s *Server) me(w http.ResponseWriter, r *http.Request) {
 	if id != nil {
 		v.Staff, v.Name, v.Rank, v.Immunity = true, id.Name, s.rankOf(x, id.SteamID), id.Immunity
 		v.Perms = id.Flags
+		// Never fails the page: without the tables, or on an error, there's just no Verification page.
+		if info, err := s.verifyInfo(r.Context()); err == nil {
+			v.Verify = info.Tables
+		}
 	}
 	writeJSON(w, http.StatusOK, v)
 }