feat(admin): add Fireworks API key and proxy to admin manifest

Registers FIREWORKS_API_KEY / FIREWORKS_PROXY in api/admin_config FIELDS so the UI can set credentials and provider status stays accurate.

Adds admin apply test and contract guards linking PROVIDER_CATALOG to FIELD_BY_KEY; updates .env.example.

.env.example

@@ -26,6 +26,10 @@ OPENCODE_API_KEY=""
 ZAI_API_KEY=""
 
 
+# Fireworks AI Config (OpenAI-compatible Chat Completions at api.fireworks.ai/inference/v1)
+FIREWORKS_API_KEY=""
+
+
 # LM Studio Config (local provider, no API key required)
 LM_STUDIO_BASE_URL="http://localhost:1234/v1"
 
@@ -40,7 +44,7 @@ OLLAMA_BASE_URL="http://localhost:11434"
 
 # All Claude model requests are mapped to these models, plain model is fallback
 # Format: provider_type/model/name
-# Valid providers: "nvidia_nim" | "open_router" | "deepseek" | "lmstudio" | "llamacpp" | "ollama" | "kimi" | "wafer" | "opencode" | "zai"
+# Valid providers: "nvidia_nim" | "open_router" | "deepseek" | "lmstudio" | "llamacpp" | "ollama" | "kimi" | "wafer" | "opencode" | "zai" | "fireworks"
 MODEL_OPUS=
 MODEL_SONNET=
 MODEL_HAIKU=
@@ -59,6 +63,7 @@ FCC_SMOKE_MODEL_KIMI=
 FCC_SMOKE_MODEL_WAFER=
 FCC_SMOKE_MODEL_OPENCODE=
 FCC_SMOKE_MODEL_ZAI=
+FCC_SMOKE_MODEL_FIREWORKS=
 FCC_SMOKE_NIM_MODELS=
 FCC_SMOKE_NIM_EXTRA_MODELS=
 FCC_SMOKE_OPENROUTER_FREE_MODELS=
@@ -84,6 +89,7 @@ KIMI_PROXY=""
 WAFER_PROXY=""
 OPENCODE_PROXY=""
 ZAI_PROXY=""
+FIREWORKS_PROXY=""
 
 PROVIDER_RATE_LIMIT=1
 PROVIDER_RATE_WINDOW=3