feat: add JSON-LD Place structured data to city pages (#120)

[aryansk]

What

City pages now emit one schema.org JSON-LD <script type="application/ld+json"> block per place, exactly as #120 specifies.

• @type picks a specific subtype where one genuinely fits — Library, GovernmentOffice, Airport — and falls back to Place otherwise
• name, address, geo (GeoCoordinates with latitude/longitude), and url pointing at the place's map deep link (/map?place=<id>)
• Only real dataset fields are emitted. Places without an address omit it; places with missing or non-finite coordinates omit geo entirely — never nulls, never placeholders, so the structured data cannot misrepresent the page

How it was verified

• New unit tests (src/lib/jsonld.test.ts, 11 tests) cover the type mapping, the deep link, and the "omit rather than fake" rules from the acceptance criteria
• npx vitest run — 63/63 pass (incl. 11 new)
• npx eslint on changed files — clean
• npm run build — clean; checked the generated static HTML: 27 valid JSON-LD blocks on /city/mumbai with real data (Library, Airport, GovernmentOffice subtypes all present), and address-less places correctly emit name/geo/url only
• All emitted blocks are parseable JSON

Notes

I can't attach a Rich Results Test screenshot from here (no browser), but every block is plain schema.org Place-family data with only genuinely-held fields, so the test should report no errors — happy to adjust if a manual run surfaces anything.

Closes#120

[vercel]

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[shauryagangrade]

Thanks for the thorough work and the tests — this looks good overall. CI’s typecheck is failing on a small TypeScript issue in the new tests (TS2352): the tests create Place-like objects with lat/lng set to undefined and then assert them to type Place, which tsc rejects.

Minimal fix
Replace the two direct casts to Place with a two-step cast via unknown to preserve the test intent while satisfying the type checker.

Suggested patch (ready to paste):

- const withoutLat = { ...place(), lat: undefined } as Place;+ const withoutLat = ({ ...place(), lat: undefined } as unknown) as Place;
expect(placeJsonLd(withoutLat)).not.toHaveProperty("geo");
- const withoutLng = { ...place(), lng: undefined } as Place;+ const withoutLng = ({ ...place(), lng: undefined } as unknown) as Place;
expect(placeJsonLd(withoutLng)).not.toHaveProperty("geo");

Suggested commit message
test: fix TS2352 in jsonld.test.ts by casting via unknown

Next steps

• Could you apply that small change and push it to this branch? CI should then pass and we can move this PR out of draft.
• If you’d like, I can push the patch as a follow-up commit or open a tiny PR with just this test fix — tell me which you prefer.

Thanks again — low-risk change and tests look comprehensive; once CI is green this should be good to merge.