Remove the on demand database backup and database.data_store

[epompeii]

The on demand database backup predates continuous replication and is unused. Its config section, database.data_store, took an AWS S3 access point ARN and was the only reason bencher_schema depended on the AWS SDK. Continuous replication under plus.disaster_recovery is the supported path.

Changes

• POST /v0/server/backup and its OPTIONS handler are removed, and the OpenAPI spec is regenerated.
• bencher server backup is removed from the CLI.
• database.data_store and its types are removed from the server config; bencher_schema drops aws-sdk-s3 and aws-credential-types, and the root manifest drops async-compression and rusqlite, which had no user left. camino becomes a plus dependency of bencher_schema, its only remaining user being plus-gated, and tokio's fs feature goes with the last tokio::fs call.
• The manual backup workflow is deleted.
• Docs in all 9 languages lose the Backups section and its CLI chunks; the database config reference and the shared example lose data_store; the disaster recovery pages no longer refer to backups, and the self-hosted skill links disaster recovery to its explanation page.
• A test pins that a database section still carrying data_store deserializes with its other fields intact, so a stale config never fails to boot.

Breaking changes

• POST /v0/server/backup and bencher server backup are gone.
• A config that still carries database.data_store is ignored. Remove the section.

Second of a stack of three, on top of the plus.disaster_recovery rename. The last PR moves the container registry storage onto object_store, at which point the AWS SDK leaves the workspace.

[github-actions]

Bencher Report

Project	Bencher
Branch	u/ep/s3-r2/server-backup
Testbed	intel-v1

Click to view all benchmark results

Benchmark	Latency	Benchmark Result microseconds (µs) (Result Δ%)	Upper Boundary microseconds (µs) (Limit %)
Adapter::Json	📈 view plot 🚷 view threshold	5.33 µs (+5.48%) Baseline: 5.05 µs	6.16 µs (86.49%)
Adapter::Magic (JSON)	📈 view plot 🚷 view threshold	5.15 µs (+5.52%) Baseline: 4.88 µs	5.83 µs (88.23%)
Adapter::Magic (Rust)	📈 view plot 🚷 view threshold	26.74 µs (-0.79%) Baseline: 26.95 µs	30.12 µs (88.77%)
Adapter::Rust	📈 view plot 🚷 view threshold	4.67 µs (+7.66%) Baseline: 4.33 µs	6.65 µs (70.19%)
Adapter::RustBench	📈 view plot 🚷 view threshold	4.66 µs (+7.58%) Baseline: 4.33 µs	6.64 µs (70.12%)

🐰 View full continuous benchmarking report in Bencher