feat: add MCP server templates and deployment infrastructure

Introduce a Helm-chart-like template system for MCP servers. Templates are
YAML files in templates/ that get seeded into the DB on startup. Users can
browse them with `mcpctl get templates`, inspect with `mcpctl describe
template`, and instantiate with `mcpctl create server --from-template=`.

Also adds Portainer deployment scripts, mcplocal systemd service,
Streamable HTTP MCP endpoint, and RPM packaging for mcpctl-local.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

templates/slack.yaml

@@ -0,0 +1,10 @@
+name: slack
+version: "1.0.0"
+description: Slack MCP server for reading channels, messages, and user info
+packageName: "@anthropic/slack-mcp"
+transport: STDIO
+repositoryUrl: https://github.com/modelcontextprotocol/servers/tree/main/src/slack
+env:
+  - name: SLACK_BOT_TOKEN
+    description: Slack bot token (xoxb-...)
+    required: true