Add Nostr release publishing to OpenWrt package workflow

[Origami74]

Add Nostr release publishing to OpenWrt package workflow

Publishes .ipk packages to Blossom and announces them as NIP-94 events on Nostr relays, giving the project a decentralized release distribution channel alongside GitHub Releases.

Changes

• Versioning job — derives package version from git tags or branch+height+hash, detects release channel (stable/beta/alpha/dev)
• Blossom upload — uploads built .ipk to blossom.primal.net with NIP-98 auth
• NIP-94 event — publishes file metadata (hash, filename, architecture, version, channel) to four relays
• Relay verification — confirms event propagation after publishing
• Signing key resolution — uses HIVE_CI_NSEC from env/secrets, falls back to ephemeral keypair
• act compatibility — replaces setup-zig GitHub Action with direct curl + tar install to avoid tool-cache race conditions on local act runners
• Pinned zig at 0.13.0 for reproducible cross-compilation

Workflow structure

determine-versioning → build (per-arch matrix) → publish-nostr (per-arch) → release (tags only)

Test plan

• Push to branch, verify both arch builds complete and print SHA-256 hashes
• Verify NIP-94 events appear on at least one relay (check build summary output)
• Run locally with act to confirm zig install and build succeed