Add Namecoin Core app

[mstrofnone]

Adds Namecoin Core — the first Bitcoin fork, powering decentralized DNS and identity.

• Full node with blockchain validation
• Name registration, lookup, update, and renewal via RPC
• Built-in wallet for NMC transactions
• Merged mining support
• Web UI for node status and name management
• Configurable pruning

[github-actions]

❌   Linting failed with 3 errors   ❌

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Linting Results

Severity	File	Description
❌	namecoin/docker-compose.yml	Invalid image name "ghcr.io/mstrofnone/namecoin-core-umbrel:30.2": Images should be named like "<name>:<version-tag>@<sha256>"
❌	namecoin/docker-compose.yml	Invalid image name "ghcr.io/mstrofnone/namecoin-core-umbrel-web:30.2": Images should be named like "<name>:<version-tag>@<sha256>"
ℹ️	namecoin/docker-compose.yml	Mounted file/directory "/namecoin/data/namecoind" doesn't exist: The volume "${APP_DATA_DIR}/data/namecoind:/data/.namecoin" tries to mount the file/directory "/namecoin/data/namecoind", but it is not present. This can lead to permission errors!
ℹ️	namecoin/docker-compose.yml	External port mapping "${APP_NAMECOIN_P2P_PORT}:8334": Port mappings may be unnecessary for the app to function correctly. Docker's internal DNS resolves container names to IP addresses within the same network. External access to the web interface is handled by the app_proxy container. Port mappings are only needed if external access is required to a port not proxied by the app_proxy, or if an app needs to expose multiple ports for its functionality (e.g., DHCP, DNS, P2P, etc.).
❌	namecoin/docker-compose.yml	Invalid image name "ghcr.io/mstrofnone/namecoin-core-umbrel:30.2": Error: HTTP 401 for ghcr.io/mstrofnone/namecoin-core-umbrel:30.2: {"errors":[{"code":"UNAUTHORIZED","message":"authentication required"}]}

Legend

Symbol	Description
❌	Error: This must be resolved before this PR can be merged.
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