Use local copy of the Persona sign in button

Dependencies

• [2] JFW656FT Add a flag to enable Persona support
• [3] VVRM3EGC Link to both the Persona and legacy sign in
• [4] DV43UILU Don't float the search bar to the right in collapsed mode
• [*] D5QIOJGP * Move everything up one directory.
• [*] QL55ECJ6 - adapted ui for hydra, more in line with nixos.org website

Change contents

• file addition: persona_sign_in_blue.png (----------)
  [6.2196]
• replacement in src/root/topbar.tt at line 130
  [2.748]→[2.748:867](∅→∅)
  − <img src="https://developer.mozilla.org/files/3963/persona_sign_in_blue.png" alt="Sign in with Persona" />
  [2.748]

  [2.867]
  + <img src="[% c.uri_for("/static/images/persona_sign_in_blue.png") %]" alt="Sign in with Persona" />