refactor: remove unused server scaffolding

[KyleDerZweite]

Applied

• Replaced the check script wrapper with direct Cargo and cargo deny checks.
• Removed five unused template workspace crates and unused manifest edges. Ed25519 RNG features are now explicit after removing hidden vodozemac feature coupling.
• Removed write only device OTK count updates and their stale SQLx cache entry. OTK responses still query one_time_keys directly.
• Removed duplicate client stubs, the duplicate room state query, LoginResponse, SyncRoom, the logout hash, the wake payload, and the ignored media flag.

Retained and compatibility

• Kept migrations/002_otk_counts.sql unchanged. Existing tables and data remain but are no longer read or written. A future approved migration can remove the table if data removal is authorized.
• Matrix HTTP responses remain unchanged.
• The Rust API no longer exposes LoginResponse, SyncRoom, or WakeEvent. No repository callers exist. External consumers should use JSON login responses, room tuples, and a unit wake message.
• The workspace no longer exposes the five template packages. Add a package again when it has real behavior and a caller.
• scripts/check.sh no longer accepts modes. Run individual Cargo commands for a smaller check or formatting fix.
• No code finding was skipped. Only deletion of existing migration history and database data was intentionally retained.

Checks

• Cargo formatting for all workspace packages in check mode: passed.
• Bash syntax for scripts/check.sh: passed.
• Cargo check for the locked workspace, every target and feature, with SQLx offline: passed.
• Cargo tests for every workspace target and feature with SQLx offline: passed, 9 tests.
• Cargo Clippy for every workspace target and feature with warnings denied and SQLx offline: passed.
• Cargo metadata with locked resolution and no dependencies: passed.
• Cargo deny for advisories, licenses, bans, and sources: failed on preexisting RUSTSEC-2026-0221 for event-listener 5.4.1. The base lockfile contains the same version. Licenses, bans, and sources passed.