fix(extensions-library): declare required API keys in weaviate and open-interpreter manifests

[yasinBursali]

What

Adds missing env_vars entries for required API keys in weaviate and open-interpreter manifests.

Why

Both services use Docker's :? syntax to require API keys at startup (WEAVIATE_API_KEY and OPEN_INTERPRETER_API_KEY), but neither manifest declared these in env_vars. Setup wizards and CLIs reading manifests had no way to prompt users for these keys, causing cryptic Docker failures like WEAVIATE_API_KEY must be set.

How

• weaviate/manifest.yaml: Replaced env_vars: [] with WEAVIATE_API_KEY entry (required: true, secret: true)
• open-interpreter/manifest.yaml: Added env_vars section with OPEN_INTERPRETER_API_KEY entry (required: true, secret: true)

Both entries include descriptive text explaining the key is required and compose will fail without it.

Scope

All changes within resources/dev/extensions-library/services/weaviate/ and resources/dev/extensions-library/services/open-interpreter/.

Testing

• Schema validation passes for both manifests
• Verified compose files — only :? variables are the two declared keys; other env vars use :- (optional defaults) and don't need manifest entries
• No compose or runtime changes

Merge Order

No dependencies on other open PRs. Can merge independently.

[yasinBursali]

Closing: CG review found that neither WEAVIATE_API_KEY nor OPEN_INTERPRETER_API_KEY are referenced in the compose files. Weaviate has AUTHENTICATION_ANONYMOUS_ACCESS_ENABLED=true and open-interpreter has a hardcoded api_key. This PR is superseded by PR #570 which adds the weaviate env_var alongside an actual setup.sh hook.