feat: Phase 3 - architecture & maintainability

- Split 1474-line dashboard.go into 5 domain files (clients, providers, users, system)
- Unit tests for ModelRegistry.FindModel and CalculateCost
- go mod tidy + verify (deps clean)
- .gitignore excludes tool cache dirs (.pi-lens/, .opencode/)

internal/providers/ollama.go

@@ -12,7 +12,6 @@ import (
 	"github.com/go-resty/resty/v2"
 	"gophergate/internal/config"
 	"gophergate/internal/models"
-	"log/slog"
 )
 
 type OllamaProvider struct {
@@ -53,18 +52,15 @@ func (p *OllamaProvider) ChatCompletion(ctx context.Context, req *models.Unified
 		Post(url)
 
 	if err != nil {
-		fmt.Printf("[Ollama] Request error: %v\n", err)
 		return nil, fmt.Errorf("request failed: %w", err)
 	}
 
 	if !resp.IsSuccess() {
-		fmt.Printf("[Ollama] API error %d: %s\n", resp.StatusCode(), resp.String())
 		return nil, fmt.Errorf("Ollama API error (%d): %s", resp.StatusCode(), resp.String())
 	}
 
 	var respJSON map[string]interface{}
 	if err := json.Unmarshal(resp.Body(), &respJSON); err != nil {
-		fmt.Printf("[Ollama] Parse error: %v\n", err)
 		return nil, fmt.Errorf("failed to parse response: %w", err)
 	}
 
@@ -99,7 +95,6 @@ func (p *OllamaProvider) ChatCompletionStream(ctx context.Context, req *models.U
 		defer close(ch)
 		err := StreamOllama(resp.RawBody(), ch, req.Model)
 		if err != nil {
-			fmt.Printf("Stream error: %v\n", err)
 		}
 	}()