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>

config.example.toml

@@ -8,9 +8,10 @@
 #
 #  Location: $CODECRAFT_CONFIG, otherwise <data_dir>/config.toml (Docker: /data/config.toml)
 #
-#  Secrets: any string value may reference environment variables with ${NAME},
-#  e.g. api_key = "${ANTHROPIC_API_KEY}". Prefer this over literal keys – keys
-#  entered in the UI are stored here in plain text.
+#  Keys and tokens are entered in the web UI (Settings) and stored here, readable
+#  for admins and included in backups. Any string value may also reference an
+#  environment variable as ${NAME}; Settings → Config file moves such values
+#  into this file.
 # =============================================================================
 
 [server]
@@ -47,7 +48,7 @@ currency = "USD"
 # proxy's body limit (e.g. Nginx client_max_body_size) does not apply.
 max_upload_mb = 500
 # Bearer token for Prometheus at GET /metrics (empty = /metrics disabled).
-# metrics_token = "${CODECRAFT_METRICS_TOKEN}"
+# metrics_token = "a-long-random-string"
 
 
 # -----------------------------------------------------------------------------
@@ -81,7 +82,7 @@ max_upload_mb = 500
 [providers.anthropic]
 kind = "anthropic"
 base_url = "https://api.anthropic.com/v1"
-api_key = "${ANTHROPIC_API_KEY}"
+api_key = "" # set in Settings
 # Current Claude models think adaptively; "effort" controls depth and cost.
 # Prices: Anthropic list prices in USD per 1M tokens (Nov 2026) – adjust if needed.
 models = [
@@ -97,25 +98,25 @@ models = [
 [providers.gemini]
 kind = "openai"
 base_url = "https://generativelanguage.googleapis.com/v1beta/openai"
-api_key = "${GEMINI_API_KEY}"
+api_key = "" # set in Settings
 models = []          # discovered automatically
-enabled = false      # set to true once GEMINI_API_KEY is available
+enabled = false      # enable once the key is set
 
 # opencode Go subscription (OpenAI-compatible endpoint for most models).
 # Current model list: https://opencode.ai/inference/go/v1/models
 [providers.opencode-go]
 kind = "openai"
 base_url = "https://opencode.ai/inference/go/openai/v1"
-api_key = "${OPENCODE_API_KEY}"
+api_key = "" # set in Settings
 models = []
 enabled = false
 
-# fal.ai – OpenRouter-backed LLM router. fal expects "Authorization: Key <FAL_KEY>".
+# fal.ai – OpenRouter-backed LLM router. fal expects "Authorization: Key <key>".
 # NOTE: verify base_url against the fal docs for your account.
 [providers.fal]
 kind = "openai"
 base_url = "https://fal.run/openrouter/router/openai/v1"
-api_key = "${FAL_KEY}"
+api_key = "" # set in Settings
 auth_prefix = "Key "
 models = [
   { id = "google/gemini-2.5-flash", context = 1000000, max_output = 32000, vision = true },
@@ -151,7 +152,7 @@ enabled = false
 # [mcp.trilium]
 # type = "http"
 # url = "https://notes.example.org/mcp"
-# headers = { Authorization = "Bearer ${TRILIUM_TOKEN}" }
+# headers = { Authorization = "Bearer <token>" }
 
 # [mcp.filesystem]
 # type = "stdio"
@@ -243,7 +244,7 @@ generate_image = "ask"   # costs money per image
 [images]
 enabled = false
 base_url = "https://fal.run"
-api_key = "${FAL_KEY}"
+api_key = "" # set in Settings
 default_model = "fal-ai/flux/schnell"
 output_dir = "generated"
 # The agent drafts with a "preview" model, asks which draft to refine, then
@@ -288,7 +289,7 @@ cookie_secure = "auto"
 enabled = false
 issuer = "https://auth.example.org/application/o/codecraft/"
 client_id = "codecraft"
-client_secret = "${OIDC_CLIENT_SECRET}"
+client_secret = "" # set in Settings
 scopes = ["openid", "profile", "email", "groups"]
 username_claim = "preferred_username"
 groups_claim = "groups"
@@ -309,7 +310,7 @@ button_label = "Single sign-on"
 # -----------------------------------------------------------------------------
 [search]
 # "duckduckgo" (no key, may be rate-limited), "searxng" (self-hosted, set url),
-# "brave" or "tavily" (api_key, e.g. "${BRAVE_API_KEY}")
+# "brave" or "tavily" (set api_key in Settings)
 provider = "duckduckgo"
 url = ""
 api_key = ""