chore: relicense from BSL-1.1 to dual MIT/Apache-2.0

[backnotprop]

Summary

• Replaces BSL-1.1 with dual MIT / Apache-2.0 license (user's choice)
• Copyright holder updated to N0, INC.
• Adds standard contribution clause (contributions dual-licensed under the same terms)

Files changed

File	Change
LICENSE	Deleted — old BSL-1.1
LICENSE-MIT	New — MIT License, Copyright 2025 N0, INC.
LICENSE-APACHE	New — Apache License 2.0, Copyright 2025 N0, INC.
package.json	"license": "MIT OR Apache-2.0"
apps/opencode-plugin/package.json	"license": "MIT OR Apache-2.0"
README.md	License section updated with dual-license + contribution clause
CONTRIBUTING.md	Replaced BSL/CLA with dual-license + contribution clause
apps/opencode-plugin/README.md	Footer updated

Test plan

• Verify LICENSE-MIT and LICENSE-APACHE contain correct full license text
• Verify no remaining references to BSL-1.1 in non-node_modules files
• Verify SPDX expression MIT OR Apache-2.0 in both package.json files
• npm publish dry-run for opencode plugin passes license validation

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