opencode prices and Go limits, settings out of .env

- Fetch prices for opencode (Zen and Go) incl. limits, image input, reasoning,
  long-context tiers and peak-hour/date factors; costs apply them per request
- Record the cost opencode reports per response; track Go allowance in 5h/7d/month
  windows against a provider plan limit (budget table, status overlay)
- Settings → Config file: move values of ${NAME} references into the config
- Examples, presets and forms keep keys in the config instead of .env

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/whatsnew.ts

@@ -3,6 +3,18 @@
  * under "unreleased"; scripts/release.sh renames the key to the release version.
  */
 export const WHATS_NEW: Record<string, { en: string[]; de: string[] }> = {
+  unreleased: {
+    en: [
+      "opencode: “Fetch prices” fills in prices including long-context and peak-hour pricing",
+      "Settings → Config file: move keys from environment variables into the configuration",
+      "opencode: real costs per request; Go plan usage (5 hours, week, month) in budgets and status",
+    ],
+    de: [
+      "opencode: „Preise holen“ übernimmt Preise inklusive Long-Context- und Spitzenzeit-Preisen",
+      "Einstellungen → Config-Datei: Keys aus Umgebungsvariablen in die Konfiguration übernehmen",
+      "opencode: echte Kosten pro Anfrage; Go-Plan-Verbrauch (5 Stunden, Woche, Monat) in Budget und Status",
+    ],
+  },
   "202611-00001": {
     en: [
       "Status LEDs in the sidebar for server, models and MCP – click them for details",