feat: allow configuring the dashboard listen address in config.toml

[chenqianhe]

Problem

observer start currently allows the dashboard listen address to be changed only with the per-run --dashboard-addr flag. The default 127.0.0.1:8081 is hard-coded, and unlike [proxy].port, there is no durable config.toml setting.

This is inconvenient for launchd/systemd services, machines where port 8081 is already occupied, and installations that want all runtime settings managed from one config file.

Proposed configuration

For example:

[dashboard]
addr = "127.0.0.1:8082"

A split bind / port shape would also work if that better matches the project conventions.

Suggested precedence:

1. observer start --dashboard-addr ...
2. [dashboard].addr (and the normal OBSERVER_DASHBOARD_ADDR environment override)
3. Existing default: 127.0.0.1:8081

Acceptance criteria

• observer start reads the dashboard address from config.toml.
• The existing --dashboard-addr flag remains backward compatible and overrides the config value.
• The Settings UI exposes the field and marks it as restart-required.
• The standalone observer dashboard command can use the same configured default while retaining its --addr / --port overrides.
• Documentation and configuration tests cover the new setting.

[marmutapp]

Hey @chenqianhe ,

Thanks for the request. It is Implemented in the current release, with the precedence you proposed:

[dashboard] 
addr = "127.0.0.1:8082"

Resolution order --dashboard-addr flag > OBSERVER_DASHBOARD_ADDR env > config > default, fully backward-compatible flag.

The standalone observer dashboard command shares the configured default (its --addr/--port still win). The value is validated as host:port with a numeric port in 1–65535 at load and when saved from the dashboard Settings page (which shows the field flagged restart-required), and a malformed env value is dropped with a warning rather than failing startup.

Hope that helps !