SQLite storage baseline

[JSYoo5B]

Summary

• Adds SQLite as the first durable repository target.
• Implements SQLite repositories for image, compute servers, and volumes.
• Adds persistence coverage for image repository behavior.

Main Review Points

• SQLite schema creation and repository behavior.
• Store-layer error handling and persistence semantics.
• Dependency footprint from the SQLite driver.

Verification

• go test ./...

[JSYoo5B]

SQLite schema creation is colocated with the repository implementation. That keeps the first durable store self-contained, while the app service still only sees the repository interface.

[JSYoo5B]

The current repository interface returns the created model without an error, so this implementation panics on unexpected DB failures. This is acceptable for the current narrow slice, but it is a design point to revisit when store errors need to become app-level responses.

[JSYoo5B]

The sequence column is used to preserve insertion order for list responses. This mirrors the earlier in-memory ids slice and avoids nondeterministic map iteration in tests.