feat: add project export and import functionality

- Implemented `pcli project export` command to export project hierarchy as JSON.
- Added `pcli project import` command to import project data from JSON.
- Created user client to fetch user details for comment attribution.
- Introduced new data structures for export and import processes.
- Ensured name-based references in exports and handled conflicts during imports.
- Added versioning and progress reporting for import operations.
- Updated documentation and specifications for new features.

examples/skills/kanban/SKILL.md

@@ -1,5 +1,5 @@
 ---
-name: example-skill
+name: planka-skill
 description: Manage Planka project boards using the pcli CLI. Use when the user wants to interact with Planka boards, cards, lists, tasks, labels, or comments.
 compatibility: Requires pcli binary in PATH and PLANKA_URL + PLANKA_API_KEY environment variables set
 metadata:
@@ -23,7 +23,7 @@ Ensure `jq` is installed.
 
 ## Global Flags
 
-All commands accept: `--format json|table`, `--url <url>`, `--api-key <key>`, `--log-level debug|info|warn|error`
+All commands (apart from import/export) accept: `--format json|table`, `--url <url>`, `--api-key <key>`, `--log-level debug|info|warn|error`
 
 ## Commands
 
@@ -40,8 +40,21 @@ Returns summary of all boards, lists, and card counts (open/closed per list).
 ```bash
 pcli project list
 pcli project get <project-id>
+pcli project create --name "Name" --type private   # type: private or shared
+pcli project delete <project-id>
+
+# Export/Import
+pcli project export <project-id-or-name> [--board <name-or-id>] > backup.json
+pcli project import --file backup.json
+pcli project import < backup.json
 ```
 
+Export outputs a portable JSON file (names, not IDs). Import creates all resources with fresh IDs.
+Import fails if the project+board name combination already exists on the target.
+Comments are exported with `(Original comment by <username>)` prefix for attribution.
+
+**Note:** Export outputs its own envelope format (`{version, exportedAt, project}`) directly — not the standard `{data, error}` envelope. Import progress and errors go to stderr.
+
 ### Boards
 
 ```bash
@@ -168,3 +181,16 @@ pcli card list --list <source-list-id> | jq -r '.data[].id' | while read id; do
   pcli card move $id --list <target-list-id>
 done
 ```
+
+### Export and import a project
+
+```bash
+# Export entire project
+pcli project export "My Project" > project-backup.json
+
+# Export single board
+pcli project export "My Project" --board "Sprint Board" > board-backup.json
+
+# Import to another instance (or same instance if project+board combo doesn't exist)
+pcli project import --file project-backup.json
+```