feat: implement custom fields, gantt view, calendar view, and file encryption

- Custom Fields (FEAT-001):
  - CustomField and TaskCustomValue models with formula support
  - CRUD API for custom field management
  - Formula engine for calculated fields
  - Frontend: CustomFieldEditor, CustomFieldInput, ProjectSettings page
  - Task list API now includes custom_values
  - KanbanBoard displays custom field values

- Gantt View (FEAT-003):
  - TaskDependency model with FS/SS/FF/SF dependency types
  - Dependency CRUD API with cycle detection
  - start_date field added to tasks
  - GanttChart component with Frappe Gantt integration
  - Dependency type selector in UI

- Calendar View (FEAT-004):
  - CalendarView component with FullCalendar integration
  - Date range filtering API for tasks
  - Drag-and-drop date updates
  - View mode switching in Tasks page

- File Encryption (FEAT-010):
  - AES-256-GCM encryption service
  - EncryptionKey model with key rotation support
  - Admin API for key management
  - Encrypted upload/download for confidential projects

- Migrations: 011 (custom fields), 012 (encryption keys), 013 (task dependencies)
- Updated issues.md with completion status

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

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

frontend/package-lock.json

@@ -8,7 +8,13 @@
       "name": "pjctrl-frontend",
       "version": "0.1.0",
       "dependencies": {
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+        "@fullcalendar/daygrid": "^6.1.20",
+        "@fullcalendar/interaction": "^6.1.20",
+        "@fullcalendar/react": "^6.1.20",
+        "@fullcalendar/timegrid": "^6.1.20",
         "axios": "^1.6.0",
+        "frappe-gantt": "^1.0.4",
         "react": "^18.2.0",
         "react-dom": "^18.2.0",
         "react-router-dom": "^6.21.0"
@@ -695,6 +701,57 @@
         "node": ">=12"
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+      "license": "MIT",
+      "peer": true,
+      "dependencies": {
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+    "node_modules/@fullcalendar/daygrid": {
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+      "license": "MIT",
+      "peerDependencies": {
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+    "node_modules/@fullcalendar/interaction": {
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+      "license": "MIT",
+      "peerDependencies": {
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+    "node_modules/@fullcalendar/react": {
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+      "license": "MIT",
+      "peerDependencies": {
+        "@fullcalendar/core": "~6.1.20",
+        "react": "^16.7.0 || ^17 || ^18 || ^19",
+        "react-dom": "^16.7.0 || ^17 || ^18 || ^19"
+      }
+    },
+    "node_modules/@fullcalendar/timegrid": {
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+      "resolved": "https://registry.npmjs.org/@fullcalendar/timegrid/-/timegrid-6.1.20.tgz",
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+      "license": "MIT",
+      "dependencies": {
+        "@fullcalendar/daygrid": "~6.1.20"
+      },
+      "peerDependencies": {
+        "@fullcalendar/core": "~6.1.20"
+      }
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     "node_modules/@jridgewell/gen-mapping": {
       "version": "0.3.13",
       "resolved": "https://registry.npmjs.org/@jridgewell/gen-mapping/-/gen-mapping-0.3.13.tgz",
@@ -1471,6 +1528,12 @@
         "node": ">= 6"
       }
     },
+    "node_modules/frappe-gantt": {
+      "version": "1.0.4",
+      "resolved": "https://registry.npmjs.org/frappe-gantt/-/frappe-gantt-1.0.4.tgz",
+      "integrity": "sha512-N94OP9ZiapaG5nzgCeZdxsKP8HD5aLVlH5sEHxSNZQnNKQ4BOn2l46HUD+KIE0LpYIterP7gIrFfkLNRuK0npQ==",
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+    },
     "node_modules/fsevents": {
       "version": "2.3.3",
       "resolved": "https://registry.npmjs.org/fsevents/-/fsevents-2.3.3.tgz",
@@ -1746,6 +1809,16 @@
         "node": "^10 || ^12 || >=14"
       }
     },
+    "node_modules/preact": {
+      "version": "10.12.1",
+      "resolved": "https://registry.npmjs.org/preact/-/preact-10.12.1.tgz",
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+      "license": "MIT",
+      "funding": {
+        "type": "opencollective",
+        "url": "https://opencollective.com/preact"
+      }
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     "node_modules/proxy-from-env": {
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