feat(server): implement management endpoints and redis sync

Enable full resource management via API and support data plane
synchronization.

- Add CRUD handlers for Providers, Models, and Keys using DTOs
- Implement LogWriter service for asynchronous, batched audit logging
- Update SyncService to snapshot full configuration state to Redis
- Register new API routes and initialize background services
- Add configuration options for logging performance tuning

internal/dto/key.go

@@ -0,0 +1,10 @@
+package dto
+
+// KeyDTO defines payload for key creation/update.
+type KeyDTO struct {
+    ProviderID uint    `json:"provider_id"`
+    KeySecret  string  `json:"key_secret"`
+    Balance    float64 `json:"balance"`
+    Status     string  `json:"status"`
+    Weight     int     `json:"weight"`
+}

internal/dto/model.go

@@ -0,0 +1,13 @@
+package dto
+
+// ModelDTO is used for create/update of model capabilities.
+type ModelDTO struct {
+    Name              string  `json:"name"`
+    ContextWindow     int     `json:"context_window"`
+    CostPerToken      float64 `json:"cost_per_token"`
+    SupportsVision    bool    `json:"supports_vision"`
+    SupportsFunctions bool    `json:"supports_functions"`
+    SupportsToolChoice bool   `json:"supports_tool_choice"`
+    SupportsFIM       bool    `json:"supports_fim"`
+    MaxOutputTokens   int     `json:"max_output_tokens"`
+}

internal/dto/provider.go

@@ -0,0 +1,9 @@
+package dto
+
+// ProviderDTO defines inbound payload for provider creation/update.
+type ProviderDTO struct {
+    Name    string `json:"name"`
+    Type    string `json:"type"`
+    BaseURL string `json:"base_url"`
+    APIKey  string `json:"api_key"`
+}