feat(console): portfolio-by-sector screen with real category icons

/officer/portfolio — sectors first, then the enterprises inside one.

The existing enterprises screen is a flat ranked list. It answers 'who is
worst' but not 'where is the problem', and a sector is the unit a shock
actually arrives in: a feed price moves against poultry, a milk rate
against dairy. So the count of high-risk enterprises per sector is the
first thing on the page.

Icons come from lucide-react rather than hand-drawn paths — a supervisor
scans this grid before reading it, so the shape is doing the work. One
literal icon per sector: milk, egg, wheat, scissors, storefront.

Drill-down keeps the same shape as the rest of the console: band filter
chips, a ranked table with a six-month trend line, and a detail panel with
the score donut, the loan position and a link to the full risk file. Only
the trend's endpoint dot is coloured; a fully coloured line would read as
a severity gradient it does not mean.

Reads /officer/enterprises with the house demo fallback and a Demo data
pill. Verified against the live backend: 142 enterprises across five
sectors, bands and six-month trends all present.

tsc, oxlint and npm run build clean.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

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