feat: universal LLM gateway with embedded multilingual admin console

- OpenAI-compatible gateway with intelligent routing via cortiq-router (allaigate)
- Embedded build-free admin SPA at /admin: 7 languages (en/ru/de/fr/es/zh/tr),
  light/dark themes, hot config reload (no restart)
- Admin API, per-request statistics + Prometheus /metrics, secret store, playground
- English documentation (primary) with Russian translations (*.ru.md)

src/model.rs

@@ -0,0 +1,102 @@
+//! Canonical (protocol-neutral) request/response model.
+//!
+//! All incoming protocols are translated into these types, and providers translate
+//! from them. This way N protocols × M providers do not become N×M translations:
+//! each adapter only knows its own protocol ↔ canonical mapping. See docs/ARCHITECTURE.md §3.
+
+use serde::{Deserialize, Serialize};
+
+/// How to handle routing for a specific request.
+#[derive(Clone, Debug)]
+pub enum RoutingDirective {
+    /// `model = "cortiq-auto"` — ask cortiq-router and pick a model from the pool.
+    Auto { profile: Option<String> },
+    /// `model = "<real id>"` — call a specific model directly, bypassing routing.
+    Pinned { model_id: String },
+}
+
+#[derive(Clone, Debug, Serialize, Deserialize)]
+pub struct Message {
+    pub role: String, // system | user | assistant | tool
+    #[serde(default)]
+    pub content: String,
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub tool_calls: Vec<serde_json::Value>,
+}
+
+#[derive(Clone, Debug, Default)]
+pub struct GenParams {
+    pub temperature: Option<f32>,
+    pub max_tokens: Option<u32>,
+    pub top_p: Option<f32>,
+    pub stop: Vec<String>,
+    /// Fields we do not interpret but must proxy through to the provider.
+    pub passthrough: serde_json::Map<String, serde_json::Value>,
+}
+
+#[derive(Clone, Debug, Default)]
+pub struct RequestMeta {
+    pub account: String,
+    pub protocol: String,
+    pub idempotency_key: Option<String>,
+    pub traceparent: Option<String>,
+}
+
+/// Canonical form of a generation request.
+#[derive(Clone, Debug)]
+pub struct ChatRequest {
+    pub routing: RoutingDirective,
+    pub messages: Vec<Message>,
+    pub tools: Vec<serde_json::Value>,
+    pub params: GenParams,
+    pub stream: bool,
+    pub meta: RequestMeta,
+}
+
+#[derive(Clone, Debug, Serialize)]
+pub struct Usage {
+    pub prompt_tokens: u32,
+    pub completion_tokens: u32,
+    pub total_tokens: u32,
+}
+
+/// Routing metadata attached to the response (X-Cortiq-* headers and the `cortiq` field).
+#[derive(Clone, Debug, Serialize)]
+pub struct RouteInfo {
+    pub task_label: String,
+    pub complexity_score: f32,
+    pub complexity_tier: String,
+    pub selected_model: String,
+    pub route_source: String, // router | cache | fallback | pinned
+    pub router_request_id: Option<String>,
+    pub cost_usd: f64,
+    #[serde(default)]
+    pub failover: bool,
+}
+
+#[derive(Clone, Debug, Serialize)]
+pub struct Choice {
+    pub index: u32,
+    pub message: Message,
+    pub finish_reason: String,
+}
+
+/// Canonical form of a response.
+#[derive(Clone, Debug)]
+pub struct ChatResponse {
+    pub id: String,
+    pub model_used: String,
+    pub choices: Vec<Choice>,
+    pub usage: Usage,
+    pub cortiq: RouteInfo,
+}
+
+/// Decision from cortiq-router (the subset of its contract needed by the gateway).
+#[derive(Clone, Debug)]
+pub struct RouteDecision {
+    pub task_label: String,
+    pub complexity_score: f32,
+    pub complexity_tier: String,
+    pub router_request_id: Option<String>,
+    pub source: String, // router | cache | fallback
+}