Multiple issues preventing gateway tutorials from working end-to-end

### Description

Several issues in the `01-gateway/` tutorials prevent users from successfully completing the labs when
following the README instructions. These were found during end-to-end testing.

### Issues Found

**HIGH — Blocks users immediately:**

1. **CloudFormation Launch Stack URLs point to a private staging repo**
(`private-amazon-bedrock-agentcore-samples-staging`). External users clicking these buttons get 404
errors. Affects 5 READMEs (10 URLs total).

2. **Unpinned `fastmcp >= 3.2.4`** in 4 runtime apps floats to 3.4.6, which performs a PyPI version
check at startup and exceeds the gateway's 40-second sync timeout. Target sync fails with
`SYNCHRONIZE_UNSUCCESSFUL`.

**MEDIUM:**

3. **`databricks_currency_agent/app.yaml`** sets `MODEL_ID='claude-sonnet-4'` but `app.py` defaults to
`'databricks-claude-sonnet-4'` — one will point to a nonexistent endpoint.

4. **Duplicated paragraph** in `01-attach-targets/http/README.md` — same text block appears 3 times.

### Additional issues (not in this PR, documenting for tracking):

- `sensative-data-masking` directory is misspelled (should be `sensitive`)
- 13 references to `00-vpc-gateway-setup.md` which doesn't exist
- 9 references to `vpcegress/README.md` which doesn't exist
- 6+ dangling `.ipynb` links (no notebooks in repo)
- 14+ `aws bedrock-agentcore-control` commands missing `--region` flag
- Duplicate step headings in `02-mcp-target-synchronization/README.md`

### Steps to Reproduce

1. Clone the repo
2. Navigate to `01-gateway/00-optional-setup/`
4. Deploy the `labmcp` runtime → target sync timeout after 40s (fastmcp float)

### Proposed Fix

PR forthcoming with:
- Updated CloudFormation URLs to point to `awslabs/agentcore-samples` with correct path
- Pinned `fastmcp == 3.2.4` in all 4 affected `pyproject.toml` files
- Fixed `app.yaml` MODEL_ID to match `app.py` default
- Removed duplicated paragraph

### Environment

- AgentCore CLI: 0.25.0
- Python: 3.12+
- Tested: 2026-08

---

Start in the 01-gateway/ tutorial READMEs and the four affected runtime pyproject.toml files, then inspect databricks_currency_agent/app.yaml and app.py plus 01-attach-targets/http/README.md. Verify the CloudFormation links, dependency pins, matching model IDs, and removal of the repeated paragraph by following the README deployment flow and confirming the gateway tutorials work end-to-end.

Written by the indexing model from the issue text.