copy(sponsor): reframe subtitle as private financing, not ad replacement

The old copy positioned sponsoring as a substitute for ads ("instead
of ads"), but the platform still runs ads when advertising partners
are available — sponsoring and ads aren't mutually exclusive. Reframe
around the actual motivation: PawFeed is entirely privately financed,
and sponsoring helps cover ongoing costs (server hardware, software
licenses, tooling).

messages/de.json

@@ -130,7 +130,7 @@
   },
   "Sponsor": {
     "title": "PawFeed unterstützen",
-    "subtitle": "PawFeed lebt von freiwilliger Unterstützung statt Werbung. Mit deinem Beitrag hilfst du, die Plattform am Laufen zu halten — als Dankeschön bekommst du das Sponsor-Badge auf deinem Profil und bei jedem Beitrag.",
+    "subtitle": "PawFeed wird komplett privat finanziert — ganz ohne Investoren, aus eigener Tasche. Server-Hardware, Software-Lizenzen und weitere Tools verursachen laufende Kosten. Mit deinem freiwilligen Beitrag hilfst du, die Plattform am Laufen zu halten — als Dankeschön bekommst du das Sponsor-Badge auf deinem Profil und bei jedem Beitrag.",
     "oneTime": "Einmalig",
     "monthly": "Monatlich",
     "customAmountLabel": "Betrag in Euro",

messages/en.json

@@ -130,7 +130,7 @@
   },
   "Sponsor": {
     "title": "Support PawFeed",
-    "subtitle": "PawFeed runs on voluntary support instead of ads. Your contribution helps keep the platform running — as a thank-you, you get the Sponsor badge on your profile and on every post.",
+    "subtitle": "PawFeed is entirely privately financed — no investors, out of pocket. Server hardware, software licenses, and other tools mean ongoing costs. Your voluntary contribution helps keep the platform running — as a thank-you, you get the Sponsor badge on your profile and on every post.",
     "oneTime": "One-time",
     "monthly": "Monthly",
     "customAmountLabel": "Amount in Euro",