Rebrand HydraProxy tier -> Mobile (stop leaking upstream supplier)

Customer-facing site no longer names the upstream broker. Rename:
- nav + page: HydraProxy -> Mobile, /hydraproxy -> /mobile
- hydraproxy.html -> mobile.html, all 'brokered/HydraProxy' copy reworded to
  owned 'Clean Proxys' language
- dashboard: 'HydraProxy orders (broker-fulfilled)' -> 'Mobile orders'
- admin panel keeps upstream names (internal only, drjones needs them)

templates/base.html

@@ -39,7 +39,7 @@
         <a href="/">Home</a>
         <a href="/plans">Residential</a>
         <a href="/dedicated">Dedicated IPs</a>
-        <a href="/hydraproxy">HydraProxy</a>
+        <a href="/mobile">Mobile</a>
         <a href="/sms">SMS</a>
         {% if user %}<a href="/dashboard">Dashboard</a><a href="/wallet">Wallet</a><a href="/quality">Quality</a><a href="/logout">Logout</a>
         {% else %}<a href="/login">Login</a><a class="cta" href="/signup">Get proxies</a>{% endif %}