Phase 4: Extract magic numbers to constants

Create config/constants.go with centralized configuration values:
- Concurrency limits (MaxConcurrentTrelloRequests)
- Timeouts (HTTP, Google Calendar, graceful shutdown, request)
- Meal times (breakfast, lunch, dinner hours)
- Database pool settings (connections, lifetime)
- Session and rate limiting settings

Update all files to use these constants instead of hardcoded values.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

2 files changed, 5 insertions, 3 deletions

diff --git a/internal/api/http.go b/internal/api/http.go
index df28c65..d9ddf0e 100644
--- a/internal/api/http.go
+++ b/internal/api/http.go
@@ -7,7 +7,8 @@ import (
 	"fmt"
 	"io"
 	"net/http"
-	"time"
+
+	"task-dashboard/internal/config"
 )
 
 // BaseClient provides common HTTP functionality for API clients
@@ -19,7 +20,7 @@ type BaseClient struct {
 // NewBaseClient creates a new BaseClient with default settings
 func NewBaseClient(baseURL string) BaseClient {
 	return BaseClient{
-		HTTPClient: &http.Client{Timeout: 15 * time.Second},
+		HTTPClient: &http.Client{Timeout: config.HTTPClientTimeout},
 		BaseURL:    baseURL,
 	}
 }
diff --git a/internal/api/trello.go b/internal/api/trello.go
index 67ffad0..a276726 100644
--- a/internal/api/trello.go
+++ b/internal/api/trello.go
@@ -9,6 +9,7 @@ import (
 	"sync"
 	"time"
 
+	"task-dashboard/internal/config"
 	"task-dashboard/internal/models"
 )
 
@@ -170,7 +171,7 @@ func (c *TrelloClient) GetBoardsWithCards(ctx context.Context) ([]models.Board,
 
 	var wg sync.WaitGroup
 	var mu sync.Mutex // Protects writes to boards slice elements
-	sem := make(chan struct{}, 5) // Limit to 5 concurrent requests
+	sem := make(chan struct{}, config.MaxConcurrentTrelloRequests)
 
 	for i := range boards {
 		wg.Add(1)