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>

.env.example

@@ -1,11 +1,11 @@
+# Deployment settings only. API keys, MCP tokens, SSO secrets and everything else
+# are set in the web UI (Settings) and stored in the configuration file.
+
 # Optional: create the first admin on first start. Otherwise the server logs a
 # one-time setup code and you create the admin in the web UI.
 CODECRAFT_ADMIN_USER=
 CODECRAFT_ADMIN_PASSWORD=
 
-# Single sign-on client secret (see [auth.oidc] in config.toml).
-OIDC_CLIENT_SECRET=
-
 # Directory with your projects, mounted as /workspace.
 WORKSPACE=/path/to/your/projects
 
@@ -17,13 +17,6 @@ BIND_ADDR=127.0.0.1
 UID=1000
 GID=1000
 
-# Provider keys – referenced in data/config.toml as ${NAME}.
-ANTHROPIC_API_KEY=
-GEMINI_API_KEY=
-OPENCODE_API_KEY=
-FAL_KEY=
-OPENROUTER_API_KEY=
-
 # Time zone for automations (cron schedules) and timestamps, e.g. Europe/Berlin
 TZ=UTC