Add webhook logging, pagination, middleware, migrations, and prod hardening

- Webhook event logging repo and subscription webhook idempotency
- Pagination helper (echohelpers) with cursor/offset support
- Request ID and structured logging middleware
- Push client improvements (FCM HTTP v1, better error handling)
- Task model version column, business constraint migrations, targeted indexes
- Expanded categorization chain tests
- Email service and config hardening
- CI workflow updates, .gitignore additions, .env.example updates

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

internal/echohelpers/pagination.go

@@ -0,0 +1,32 @@
+package echohelpers
+
+import (
+	"strconv"
+
+	"github.com/labstack/echo/v4"
+)
+
+// ParsePagination extracts limit and offset from query parameters with bounded defaults.
+// maxLimit caps the maximum page size to prevent unbounded queries.
+func ParsePagination(c echo.Context, maxLimit int) (limit, offset int) {
+	const defaultLimit = 50
+
+	limit = defaultLimit
+	if l := c.QueryParam("limit"); l != "" {
+		if parsed, err := strconv.Atoi(l); err == nil && parsed > 0 {
+			limit = parsed
+		}
+	}
+	if limit > maxLimit {
+		limit = maxLimit
+	}
+
+	offset = 0
+	if o := c.QueryParam("offset"); o != "" {
+		if parsed, err := strconv.Atoi(o); err == nil && parsed >= 0 {
+			offset = parsed
+		}
+	}
+
+	return limit, offset
+}

internal/echohelpers/pagination_test.go

@@ -0,0 +1,77 @@
+package echohelpers
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/labstack/echo/v4"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestParsePagination(t *testing.T) {
+	tests := []struct {
+		name           string
+		query          string
+		maxLimit       int
+		expectedLimit  int
+		expectedOffset int
+	}{
+		{
+			name:           "Defaults - no query params",
+			query:          "/",
+			maxLimit:       200,
+			expectedLimit:  50,
+			expectedOffset: 0,
+		},
+		{
+			name:           "Custom values",
+			query:          "/?limit=20&offset=10",
+			maxLimit:       200,
+			expectedLimit:  20,
+			expectedOffset: 10,
+		},
+		{
+			name:           "Max limit capped",
+			query:          "/?limit=500",
+			maxLimit:       200,
+			expectedLimit:  200,
+			expectedOffset: 0,
+		},
+		{
+			name:           "Negative offset ignored",
+			query:          "/?offset=-5",
+			maxLimit:       200,
+			expectedLimit:  50,
+			expectedOffset: 0,
+		},
+		{
+			name:           "Invalid limit falls back to default",
+			query:          "/?limit=abc",
+			maxLimit:       200,
+			expectedLimit:  50,
+			expectedOffset: 0,
+		},
+		{
+			name:           "Zero limit falls back to default",
+			query:          "/?limit=0",
+			maxLimit:       200,
+			expectedLimit:  50,
+			expectedOffset: 0,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			e := echo.New()
+			req := httptest.NewRequest(http.MethodGet, tt.query, nil)
+			rec := httptest.NewRecorder()
+			c := e.NewContext(req, rec)
+
+			limit, offset := ParsePagination(c, tt.maxLimit)
+
+			assert.Equal(t, tt.expectedLimit, limit, "limit mismatch")
+			assert.Equal(t, tt.expectedOffset, offset, "offset mismatch")
+		})
+	}
+}