feat: add CPU and memory resource limits per app

- Add cpu_limit (REAL) and memory_limit (INTEGER) columns to apps table
  via migration 007
- Add CPULimit and MemoryLimit fields to App model with full CRUD support
- Add resource limits fields to app edit form with human-friendly
  memory input (e.g. 256m, 1g, 512k)
- Pass CPU and memory limits to Docker container creation via
  NanoCPUs and Memory host config fields
- Extract Docker container creation helpers (buildEnvSlice, buildMounts,
  buildResources) for cleaner code
- Add formatMemoryBytes template function for display
- Add comprehensive tests for parsing, formatting, model persistence,
  and container options

internal/models/models_test.go

@@ -781,6 +781,96 @@ func TestCascadeDelete(t *testing.T) {
 	})
 }
 
+// Resource Limits Tests.
+
+func TestAppResourceLimits(t *testing.T) { //nolint:funlen // integration test with multiple subtests
+	t.Parallel()
+
+	t.Run("saves and loads CPU limit", func(t *testing.T) {
+		t.Parallel()
+
+		testDB, cleanup := setupTestDB(t)
+		defer cleanup()
+
+		app := createTestApp(t, testDB)
+
+		app.CPULimit = sql.NullFloat64{Float64: 0.5, Valid: true}
+
+		err := app.Save(context.Background())
+		require.NoError(t, err)
+
+		found, err := models.FindApp(context.Background(), testDB, app.ID)
+		require.NoError(t, err)
+		require.NotNil(t, found)
+		assert.True(t, found.CPULimit.Valid)
+		assert.InDelta(t, 0.5, found.CPULimit.Float64, 0.001)
+	})
+
+	t.Run("saves and loads memory limit", func(t *testing.T) {
+		t.Parallel()
+
+		testDB, cleanup := setupTestDB(t)
+		defer cleanup()
+
+		app := createTestApp(t, testDB)
+
+		app.MemoryLimit = sql.NullInt64{Int64: 536870912, Valid: true} // 512m
+
+		err := app.Save(context.Background())
+		require.NoError(t, err)
+
+		found, err := models.FindApp(context.Background(), testDB, app.ID)
+		require.NoError(t, err)
+		require.NotNil(t, found)
+		assert.True(t, found.MemoryLimit.Valid)
+		assert.Equal(t, int64(536870912), found.MemoryLimit.Int64)
+	})
+
+	t.Run("null limits by default", func(t *testing.T) {
+		t.Parallel()
+
+		testDB, cleanup := setupTestDB(t)
+		defer cleanup()
+
+		app := createTestApp(t, testDB)
+
+		found, err := models.FindApp(context.Background(), testDB, app.ID)
+		require.NoError(t, err)
+		require.NotNil(t, found)
+		assert.False(t, found.CPULimit.Valid)
+		assert.False(t, found.MemoryLimit.Valid)
+	})
+
+	t.Run("clears limits when set to null", func(t *testing.T) {
+		t.Parallel()
+
+		testDB, cleanup := setupTestDB(t)
+		defer cleanup()
+
+		app := createTestApp(t, testDB)
+
+		// Set limits
+		app.CPULimit = sql.NullFloat64{Float64: 1.0, Valid: true}
+		app.MemoryLimit = sql.NullInt64{Int64: 1073741824, Valid: true} // 1g
+
+		err := app.Save(context.Background())
+		require.NoError(t, err)
+
+		// Clear limits
+		app.CPULimit = sql.NullFloat64{}
+		app.MemoryLimit = sql.NullInt64{}
+
+		err = app.Save(context.Background())
+		require.NoError(t, err)
+
+		found, err := models.FindApp(context.Background(), testDB, app.ID)
+		require.NoError(t, err)
+		require.NotNil(t, found)
+		assert.False(t, found.CPULimit.Valid)
+		assert.False(t, found.MemoryLimit.Valid)
+	})
+}
+
 // Helper function to create a test app.
 func createTestApp(t *testing.T, testDB *database.Database) *models.App {
 	t.Helper()