feat: implement soft delete, task editing fixes, and UI improvements

Backend:
- Add soft delete for spaces and projects (is_active flag)
- Add status_id and assignee_id to TaskUpdate schema
- Fix task PATCH endpoint to update status and assignee
- Add validation for assignee_id and status_id in task updates
- Fix health service to count tasks with "Blocked" status as blockers
- Filter out deleted spaces/projects from health dashboard
- Add workload cache invalidation on assignee changes

Frontend:
- Add delete confirmation dialogs for spaces and projects
- Fix UserSelect to display selected user name (valueName prop)
- Fix task detail modal to refresh data after save
- Enforce 2-level subtask depth limit in UI
- Fix timezone bug in date formatting (use local timezone)
- Convert NotificationBell from Tailwind to inline styles
- Add i18n translations for health, workload, settings pages
- Add parent_task_id to Task interface across components

OpenSpec:
- Archive add-delete-capability change

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

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

frontend/public/locales/en/settings.json

@@ -2,6 +2,21 @@
   "title": "Settings",
   "projectSettings": "Project Settings",
   "backToTasks": "Back to Tasks",
+  "mySettings": {
+    "title": "My Settings",
+    "profile": "Profile",
+    "email": "Email",
+    "department": "Department",
+    "role": "Role",
+    "workloadSettings": "Workload Settings",
+    "capacityDescription": "Set your weekly available work hours, used to calculate workload percentage.",
+    "weeklyCapacity": "Weekly Capacity",
+    "hoursPerWeek": "hours/week",
+    "capacityHelp": "Recommended: 40 hours (standard work week). Maximum: 168 hours (total hours in a week).",
+    "capacitySaved": "Capacity settings saved",
+    "capacityError": "Failed to save capacity settings",
+    "capacityInvalid": "Please enter a valid number of hours (0-168)"
+  },
   "tabs": {
     "general": "General",
     "members": "Members",
@@ -37,16 +52,58 @@
     "add": "Add Field",
     "edit": "Edit Field",
     "delete": "Delete Field",
+    "create": "Create Field",
     "fieldName": "Field Name",
+    "fieldNamePlaceholder": "e.g., Story Points, Sprint Number",
     "fieldType": "Field Type",
     "required": "Required",
+    "requiredField": "Required field",
+    "requiredHelp": "Tasks cannot be created or updated without filling in required fields.",
+    "cannotChangeType": "cannot be changed",
+    "description": "Custom fields allow you to add additional data to tasks. You can create up to 20 fields per project.",
+    "loading": "Loading custom fields...",
+    "loadError": "Failed to load custom fields",
+    "retry": "Retry",
+    "empty": "No custom fields defined yet.",
+    "emptyHint": "Click \"Add Field\" to create your first custom field.",
+    "deleteConfirmTitle": "Delete Custom Field?",
+    "deleteConfirmMessage": "This will permanently delete this field and all stored values for all tasks. This action cannot be undone.",
+    "deleting": "Deleting...",
+    "deleted": "Custom field deleted successfully",
+    "deleteError": "Failed to delete field",
+    "saving": "Saving...",
+    "saveChanges": "Save Changes",
+    "saveError": "Failed to save field",
+    "options": "Options",
+    "optionPlaceholder": "Option {{index}}",
+    "addOption": "Add Option",
+    "optionRequired": "At least one option is required for dropdown fields",
+    "formula": "Formula Expression",
+    "formulaPlaceholder": "e.g., {time_spent} / {original_estimate} * 100",
+    "formulaRequired": "Formula expression is required",
+    "formulaHelp": {
+      "intro": "Use curly braces to reference other fields:",
+      "customField": "Reference a custom number field",
+      "estimate": "Task time estimate",
+      "timeSpent": "Logged time",
+      "operators": "Supported operators: +, -, *, /"
+    },
     "types": {
       "text": "Text",
+      "textDesc": "Single line text input",
       "number": "Number",
+      "numberDesc": "Numeric value",
       "date": "Date",
-      "select": "Dropdown",
-      "multiSelect": "Multi-select",
-      "checkbox": "Checkbox"
+      "dateDesc": "Date picker",
+      "dropdown": "Dropdown",
+      "dropdownDesc": "Select from predefined options",
+      "person": "Person",
+      "personDesc": "User assignment",
+      "formula": "Formula",
+      "formulaDesc": "Calculated from other fields"
+    },
+    "validation": {
+      "nameRequired": "Field name is required"
     }
   },
   "notifications": {