chore: v0.61.0

[fylorn]

Release for #284.

• Bump the workspace version to 0.61.0 (Cargo.toml, and the workspace crates in Cargo.lock).
• Add release-notes/0.61.0.md: an opening paragraph, the upgrade notes, and one section each for safe mode with a configuration that does not load and the one-click repair.
• CONTROL_API_VERSION (37) is already at its release value on main; the request store SCHEMA is unchanged (25).

Upgrade notes in brief

• Protocol 36 → 37. Lite 2026.10.2 (core 0.60.0) does not connect to 0.61.0; sudo twcore upgrade --version 0.60.0 --restart switches a server back.
• Schema unchanged (25), history kept. Configuration format unchanged.
• Protocol: new GET /config/repair and POST /config/repair (ConfigRepair, ConfigFix, ConfigFixKind, ConfigRepairRequest); in safe mode Status.config_rejected is set from the start when the configuration does not load.
• Message codes, from diffing msg-codes.txt and every msg! between v0.60.0 and main: new config.unknown_variant, config.unknown_field, control.config_not_repairable; nothing removed; no sentence changed.

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