config: warnings in parse() emit before logging is configured (ignores logging.format/level)

[skyoo2003]

Context

Surfaced during code review of #111 (finding 5, skipped as pre-existing).

Problem

config.parse() emits slog.Warn(...) — the new dashboard deprecation warning, and the pre-existing unknown-tier / DEVCLOUD_SERVICES warnings — before setupLogging() installs the configured slog handler in cmd/devcloud/main.go.

As a result these warnings always go through the default text handler and ignore the operator's logging.format / logging.level. With logging: {format: json}, the warnings come out as plain text and break downstream JSON log parsers.

Why it was deferred

Consistent with the existing warning pattern already in parse() (not introduced by #111). A proper fix means reordering startup so logging is configured before config warnings are produced — and must avoid suppressing the warnings entirely.

Suggested fix

Options:

• Collect warnings during parse() and flush them after setupLogging(), or
• Return them from parse()/Load() for the caller to log post-setup, or
• Configure logging early enough that parse() warnings honor logging.format.

Acceptance

• With logging.format: json, config-time warnings are emitted as JSON and respect logging.level.
• No config warnings are lost.