M5 polish: dashboard query + test-shape follow-ups

[aharlap]

Track-as-issue items from the Milestone 5 closing review (none blocking):

• /dashboard calls listKeys() on every load — only needed when activities are empty; use a cheap hasKeys() or conditional query
• The equal-width funnel-track regression test pins style strings (proxy); a rendered-layout assertion would pin the original bug directly
• Empty-state branch tests are component-level; add route-level coverage when test DB isolation improves

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