feat: add observing ephemerides and Polaris

[Haeniken]

What changed

• adds observing diagnostics for the Sun, Moon, all planets and Pluto
• adds Polaris with SynScan coordinates to the Astrodome dataset
• versions and validates the scientific payload fail-closed
• documents formulae, applicability domains and planning approximations in English and Russian

Why

Observers need object position, angular size, phase, elongation, culmination and object-specific context directly alongside the 72-hour forecast and Astrodome.

Impact

Forecast 1/7 and Astrodome payloads now carry versioned observing ephemerides. Existing meteorological and Overall calculations are unchanged.

Validation

The exact deployed diff passed the production Go test, vet, build, golangci-lint and govulncheck gates. Independent scientific review found no remaining blocker or major issue. git diff --check also passed before commit.