feat(mcp): close Cloud tool coverage gaps

[joshrotenberg]

Summary

Adds 4 new Cloud MCP tools to close the remaining CLI/MCP parity gaps. Closes #773.

New tools

Tool	Type	Description
update_account_user	non_destructive	Update account user name/role
delete_account_user	destructive	Permanently delete an account user
wait_for_cloud_task	read_only	Poll async task until completion with timeout
flush_crdb_database	destructive	Flush Active-Active (CRDB) database

wait_for_cloud_task -- the high-value addition

Agents orchestrating multi-step workflows (create subscription -> wait -> create database) previously had no way to block on async Cloud operations. This tool polls a task ID every N seconds until it reaches a terminal state or times out, returning the final status.

Parameters:
  task_id: String
  timeout_seconds: u64 (default 300)
  interval_seconds: u64 (default 5)
  profile: Option<String>

Triaged out (no tool needed)

• export_cost_report: CLI convenience that combines generate + wait + download. Agents can compose this from existing tools.
• Provider accounts: Already fully covered by existing cloud_accounts tools (list, get, create, update, delete).

Test plan

• cargo fmt --all -- --check
• cargo clippy -p redisctl-mcp --all-targets --all-features -- -D warnings
• cargo test -p redisctl-mcp --all-features
• cargo check -p redisctl-mcp --no-default-features
• Annotation tests for all 4 new tools (read_only, non_destructive, destructive)