refactor: remove batch configuration mechanism

[lwshang]

Summary

The configure / get_configuration endpoints exposed three upload limits — max_batches, max_chunks, max_bytes — all defaulting to None (unlimited). Nothing ever set them: the sync-plugin, the only client and the only contract that matters, never calls configure. So the limits were always inactive and every limit check was dead code.

This removes the whole mechanism rather than keeping a config surface for a feature that did nothing in practice.

What changed

Commit 1 — remove the configuration mechanism (505 deletions)

• assets.did: dropped ConfigurationResponse / ConfigureArguments types and the get_configuration / configure endpoints
• types.rs: removed both IDL structs (including the Option<Option<u64>> tri-state)
• state.rs: removed the Configuration struct, the configuration field, both methods, and the restore line
• stable.rs: removed StableConfiguration, its two From impls, and the StableState field
• batch.rs: removed the three limit checks plus the now-dead chunk_content_total_size field and compute_last_chunk_data helper
• tests.rs: removed the configuration_methods and enforce_limits modules

Commit 2 — make create_batch infallible
With the limits gone, create_batch had no remaining error path. Dropped the Result<BatchId, String> wrapper: the State method returns BatchId directly, the wrapper builds the response without a match, and the test call sites lose their .unwrap().

Behavior

Uploads are now unbounded at the application layer — same as before in practice, since no client set these limits. Only authorized/controller principals can create batches at all, and the IC heap cap remains the backstop.

No backward-compatibility concern: pre-launch, no production instances, no persisted state to migrate.

Verification

• cargo test -p canister-core — 87 passed
• cargo test -p canister — candid-compatibility check passes (hand-edited assets.did matches generated interface)
• cargo test -p e2e — 14 passed
• cargo clippy -p canister-core -p canister --all-targets — clean

🤖 Generated with Claude Code