Replace Gorush with direct APNs/FCM integration

- Add direct APNs client using sideshow/apns2 for iOS push
- Add direct FCM client using legacy HTTP API for Android push
- Remove Gorush dependency (no external push server needed)
- Update all services/handlers to use new push.Client
- Update config for APNS_PRODUCTION flag

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

internal/push/fcm.go

@@ -0,0 +1,139 @@
+package push
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"time"
+
+	"github.com/rs/zerolog/log"
+
+	"github.com/treytartt/casera-api/internal/config"
+)
+
+const fcmEndpoint = "https://fcm.googleapis.com/fcm/send"
+
+// FCMClient handles direct communication with Firebase Cloud Messaging
+type FCMClient struct {
+	serverKey  string
+	httpClient *http.Client
+}
+
+// FCMMessage represents an FCM message payload
+type FCMMessage struct {
+	To               string            `json:"to,omitempty"`
+	RegistrationIDs  []string          `json:"registration_ids,omitempty"`
+	Notification     *FCMNotification  `json:"notification,omitempty"`
+	Data             map[string]string `json:"data,omitempty"`
+	Priority         string            `json:"priority,omitempty"`
+	ContentAvailable bool              `json:"content_available,omitempty"`
+}
+
+// FCMNotification represents the notification payload
+type FCMNotification struct {
+	Title string `json:"title,omitempty"`
+	Body  string `json:"body,omitempty"`
+	Sound string `json:"sound,omitempty"`
+	Badge string `json:"badge,omitempty"`
+	Icon  string `json:"icon,omitempty"`
+}
+
+// FCMResponse represents the FCM API response
+type FCMResponse struct {
+	MulticastID  int64       `json:"multicast_id"`
+	Success      int         `json:"success"`
+	Failure      int         `json:"failure"`
+	CanonicalIDs int         `json:"canonical_ids"`
+	Results      []FCMResult `json:"results"`
+}
+
+// FCMResult represents a single result in the FCM response
+type FCMResult struct {
+	MessageID      string `json:"message_id,omitempty"`
+	RegistrationID string `json:"registration_id,omitempty"`
+	Error          string `json:"error,omitempty"`
+}
+
+// NewFCMClient creates a new FCM client
+func NewFCMClient(cfg *config.PushConfig) (*FCMClient, error) {
+	if cfg.FCMServerKey == "" {
+		return nil, fmt.Errorf("FCM server key not configured")
+	}
+
+	return &FCMClient{
+		serverKey: cfg.FCMServerKey,
+		httpClient: &http.Client{
+			Timeout: 30 * time.Second,
+		},
+	}, nil
+}
+
+// Send sends a push notification to Android devices
+func (c *FCMClient) Send(ctx context.Context, tokens []string, title, message string, data map[string]string) error {
+	if len(tokens) == 0 {
+		return nil
+	}
+
+	msg := FCMMessage{
+		RegistrationIDs: tokens,
+		Notification: &FCMNotification{
+			Title: title,
+			Body:  message,
+			Sound: "default",
+		},
+		Data:     data,
+		Priority: "high",
+	}
+
+	body, err := json.Marshal(msg)
+	if err != nil {
+		return fmt.Errorf("failed to marshal FCM message: %w", err)
+	}
+
+	req, err := http.NewRequestWithContext(ctx, "POST", fcmEndpoint, bytes.NewReader(body))
+	if err != nil {
+		return fmt.Errorf("failed to create FCM request: %w", err)
+	}
+
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("Authorization", "key="+c.serverKey)
+
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return fmt.Errorf("failed to send FCM request: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("FCM returned status %d", resp.StatusCode)
+	}
+
+	var fcmResp FCMResponse
+	if err := json.NewDecoder(resp.Body).Decode(&fcmResp); err != nil {
+		return fmt.Errorf("failed to decode FCM response: %w", err)
+	}
+
+	// Log individual results
+	for i, result := range fcmResp.Results {
+		if result.Error != "" {
+			log.Error().
+				Str("token", truncateToken(tokens[i])).
+				Str("error", result.Error).
+				Msg("FCM notification failed")
+		}
+	}
+
+	log.Info().
+		Int("total", len(tokens)).
+		Int("success", fcmResp.Success).
+		Int("failure", fcmResp.Failure).
+		Msg("FCM batch send complete")
+
+	if fcmResp.Success == 0 && fcmResp.Failure > 0 {
+		return fmt.Errorf("all FCM notifications failed")
+	}
+
+	return nil
+}