fix: pin npm package versions in MCP integration templates (#25)

* fix: pin npm package versions in MCP integration templates

Prevent supply chain attacks by pinning exact versions instead of
using unpinned `npx -y @package` which pulls latest on every run.

23 of 25 integrations pinned. sqlite-mcp and aws skipped (packages
not found on npm registry).

* fix: use stable azure/mcp version instead of beta

integrations/slack.toml

@@ -8,7 +8,7 @@ tags = ["chat", "messaging", "team", "channels", "collaboration"]
 [transport]
 type = "stdio"
 command = "npx"
-args = ["-y", "@modelcontextprotocol/server-slack"]
+args = ["-y", "@modelcontextprotocol/server-slack@2025.4.25"]
 
 [[required_env]]
 name = "SLACK_BOT_TOKEN"