Coverage priorities 1-5: test pure functions, extract interfaces, mock-based handler tests

- Priority 1: Test NewSendEmailTask + NewSendPushTask (5 tests)
- Priority 2: Test customHTTPErrorHandler — all 15+ branches (21 tests)
- Priority 3: Extract Enqueuer interface + payload builders in worker pkg (5 tests)
- Priority 4: Extract ClassifyFile/ComputeRelPath in migrate-encrypt (6 tests)
- Priority 5: Define Handler interfaces, refactor to accept them, mock-based tests (14 tests)
- Fix .gitignore: /worker instead of worker to stop ignoring internal/worker/

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/worker/scheduler.go

@@ -1,8 +1,6 @@
 package worker
 
 import (
-	"encoding/json"
-
 	"github.com/hibiken/asynq"
 	"github.com/rs/zerolog/log"
 )
@@ -58,10 +56,7 @@ func (c *TaskClient) Close() error {
 
 // EnqueueWelcomeEmail enqueues a welcome email task
 func (c *TaskClient) EnqueueWelcomeEmail(to, firstName, code string) error {
-	payload, err := json.Marshal(WelcomeEmailPayload{
-		EmailPayload:     EmailPayload{To: to, FirstName: firstName},
-		ConfirmationCode: code,
-	})
+	payload, err := BuildWelcomeEmailPayload(to, firstName, code)
 	if err != nil {
 		return err
 	}
@@ -79,10 +74,7 @@ func (c *TaskClient) EnqueueWelcomeEmail(to, firstName, code string) error {
 
 // EnqueueVerificationEmail enqueues a verification email task
 func (c *TaskClient) EnqueueVerificationEmail(to, firstName, code string) error {
-	payload, err := json.Marshal(VerificationEmailPayload{
-		EmailPayload: EmailPayload{To: to, FirstName: firstName},
-		Code:         code,
-	})
+	payload, err := BuildVerificationEmailPayload(to, firstName, code)
 	if err != nil {
 		return err
 	}
@@ -100,11 +92,7 @@ func (c *TaskClient) EnqueueVerificationEmail(to, firstName, code string) error
 
 // EnqueuePasswordResetEmail enqueues a password reset email task
 func (c *TaskClient) EnqueuePasswordResetEmail(to, firstName, code, resetToken string) error {
-	payload, err := json.Marshal(PasswordResetEmailPayload{
-		EmailPayload: EmailPayload{To: to, FirstName: firstName},
-		Code:         code,
-		ResetToken:   resetToken,
-	})
+	payload, err := BuildPasswordResetEmailPayload(to, firstName, code, resetToken)
 	if err != nil {
 		return err
 	}
@@ -122,7 +110,7 @@ func (c *TaskClient) EnqueuePasswordResetEmail(to, firstName, code, resetToken s
 
 // EnqueuePasswordChangedEmail enqueues a password changed confirmation email
 func (c *TaskClient) EnqueuePasswordChangedEmail(to, firstName string) error {
-	payload, err := json.Marshal(EmailPayload{To: to, FirstName: firstName})
+	payload, err := BuildPasswordChangedEmailPayload(to, firstName)
 	if err != nil {
 		return err
 	}