feat(api): resolve match construction period by year

[jravani]

What

GET /api/v1/variants/{cc}/match now accepts year as an alternative to period. Exactly one of the two is required; both or neither is a 400. With year, ignis selects the period whose construction-year band contains it, scoped to the requested building type, then returns the same refurbishment-variant list as the period path. period is unchanged and backward compatible.

New GET /api/v1/periods/{cc} returns a country's bands as [{ period, year_from, year_to }], oldest first. year_from 0 and year_to 9999 are passed through as the open-ended sentinels.

How

• TabulaReader.ResolvePeriodByYear(tableName, typePrefix, year) and ListPeriods(tableName) read Code_ConstructionYearClass, Year1_Building, Year2_Building. These are already DB columns: build_db creates one per workbook header, so no loader change was needed.
• The Year1_Building = 0 / Year2_Building = 9999 open-ended bands need no special case; a plain Year1 <= year <= Year2 comparison covers them. Verified against real rows (e.g. AT.01 = 0..1918, SI.06 = 2009..9999).
• Year resolution is scoped to CC.N.TYPE, so a year with no archetype for that type (e.g. DE terraced houses have no pre-1860 band) returns an empty match list, not an error.

Tests

• Repository integration tests: band resolution including both boundaries, the open-ended newest band, and a type that lacks a band; ListPeriods ordering and sentinel passthrough.
• Handler tests: the year path, the both/neither 400, non-integer year, the empty-list case, and repo error to 500; ListPeriods success, unknown country, repo error.
• go test ./..., go test -tags integration ./internal/db/..., go vet ./..., make schema-check, and redocly lint on the OpenAPI spec all pass.

Docs

OpenAPI spec (year param, /periods path, PeriodsResponse / ConstructionPeriod schemas) and docs/api.md updated.

Closes #29

https://claude.ai/code/session_01JBfY6ZG2W52imgy2M1JGYo

[codecov-commenter]

Codecov Report

❌ Patch coverage is 89.41176% with 9 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
internal/db/repository/tabula_repository.go	80.43%	5 Missing and 4 partials ⚠️

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