Add Askardex to Node Deployment & Operations and Canton APIs SIGs

Adding Askardex (validator operator on Canton mainnet) to two SIGs:

• Node Deployment & Operations - We operate a Canton validator running Wallet and Bridge services on mainnet since Q4 2025
• Canton APIs (Ledger API, SQL API, Admin API) - We consume JSON Ledger API v2 costEstimation, participant admin traffic endpoints, and AmuletRules fee primitives daily in production

Per the contributing instructions in sig-directory.md:

If you would like to join an existing SIG, please submit a Pull Request updating this file.