Expose series/universe on the quote read path — QuoteResponse fields and filters

[DutchJaFO]

Background

#179 added the Universe → Series → Source schema and #180 populated it (75 Sources across 26
Series and 5 Universes, from a curated overlay file). Nothing reads it. QuoteResponse has no
series or universe field, and no endpoint filters on either — so the data #180 populates currently
has no read path from a quote at all.

This is the capability #169's research was originally motivated by: grouping related Sources so a
consumer can ask for "a random Star Wars quote" or display "from the Middle Earth universe" without
knowing which individual films exist. Today a consumer would have to fetch the quote, look up its
Source (#184), then look up that Source's Series (#187), then that Series' Universe (#188) — three
extra round-trips to answer a question the quote itself should be able to answer, and still no way to
filter by either.

The masterdata list endpoints (#184/#187/#188) are a different concern: they expose Series/Universe as
first-class entities to enumerate and (later) manage. This issue is about enriching and filtering the
quote read path, which none of them touch.

Depends on #183, which establishes this project's convention for an entity-scoped filter query
parameter — how it is named, parsed, validated (422 on malformed input rather than letting the
framework's binder throw), and applied to the underlying query. #183 names ?universeId= as its own
worked example, so this issue is a direct consumer of that convention rather than a place to re-decide
it. Sequencing this after #183 is what keeps the quote endpoints' filters and the masterdata
endpoints' filters from drifting into two different shapes.

Found while reviewing #180's T1 (2026-07-16): the developer's first observation on seeing a live quote
response was that it carries neither field.

What needs to be done

1. Add series and universe to QuoteResponse — populated by joining Sources.SeriesId →
   Series → Series.UniverseId → Universe. Both nullable: a standalone Source has no Series, and
   a standalone Series has no Universe (both are the common case today — only 75 of 479 Sources are
   in a Series at all).
2. Extend Sql.Quotes.SelectBase's projection with the two LEFT JOINs. They must be LEFT — a
   Source with no Series must still return its quote, not drop it from every result.
3. Add Series and Universe filters to GET /api/v1/quotes, GET /api/v1/quotes/random, and
   GET /api/v1/quotes/search, wired through SqliteQuoteService.BuildFilterWhere alongside the
   existing character/author/source filters. Follow List-endpoint shared infrastructure for the masterdata and Conversations list endpoints #183's documented filter-parameter
   convention — naming, parsing, validation, and how the filter reaches the query — rather than
   re-deciding any of it here. List-endpoint shared infrastructure for the masterdata and Conversations list endpoints #183 settles the open question of whether an entity-scoped filter is
   id-valued or name-valued; this issue adopts whatever it lands on, so the quote endpoints' filters
   and the masterdata endpoints' filters stay one pattern. Note the existing
   source/character/author filters on these same endpoints are case-insensitive contains
   matches on a name — if List-endpoint shared infrastructure for the masterdata and Conversations list endpoints #183's convention differs, the mismatch on one endpoint is worth a
   deliberate note rather than a silent inconsistency.
4. A Universe filter must match quotes across every Series in that Universe, not only Sources
   directly named by it — the join is Quote → Source → Series → Universe, so the filter applies two
   levels up. This is the main reason a Universe filter is worth having at all ("a random Middle Earth
   quote" spans both the LOTR and Hobbit Series).
5. Update README.md, addon/DOCS.md, and QuoteEndpoints.cs's [Description] attributes in the
   same commit, per this project's "Keeping API documentation in sync" rule.
6. If List-endpoint shared infrastructure for the masterdata and Conversations list endpoints #183's convention lands on an id-valued filter, it matches case-insensitively from the start per
   CLAUDE.md's "GUID/enum/id comparisons are case-insensitive by default" rule — with a
   lowercase/mixed-case regression test in the same commit, not deferred.

Expected tests

Test class	Test method	Starts
Quotinator.Engine.Tests.Services.SqliteQuoteServiceTests	GetById_SourceInSeriesWithUniverse_ResponseCarriesBoth	❌
Quotinator.Engine.Tests.Services.SqliteQuoteServiceTests	GetById_SourceWithNoSeries_ReturnsQuoteWithNullSeriesAndUniverse	❌
Quotinator.Engine.Tests.Services.SqliteQuoteServiceTests	GetById_SeriesWithNoUniverse_ReturnsSeriesWithNullUniverse	❌
Quotinator.Api.Tests.Endpoints.QuoteEndpointsTests	GetAll_SeriesFilter_ReturnsOnlyThatSeriesQuotes	❌
Quotinator.Api.Tests.Endpoints.QuoteEndpointsTests	GetAll_UniverseFilter_ReturnsQuotesAcrossEverySeriesInThatUniverse	❌
Quotinator.Api.Tests.Endpoints.QuoteEndpointsTests	GetRandom_UniverseFilter_ReturnsOnlyThatUniverseQuotes	❌
Quotinator.Data.Tests.Security.SqlQueryGuardTests	AssembledQuery_PassesAggregateGuard (existing — new filter cases added to AssembledQueryCases)	✅

Definition of done

• All expected tests listed above start red before implementation
• All requirements implemented
• All expected tests pass (green)
• No regression in related tests
• Findings summarised in a closing comment

[DutchJaFO]

Released in v1.8.0.

#	Status	Requirement	Method	Verification
1-5	✅	QuoteResponse.Series/Universe populated correctly (with/without Universe, no Series, soft-deleted Series/Universe never leaks)	Unit test	SqliteQuoteServiceTests.GetById_*
6-8	✅	Series/Universe filters on /quotes, /random, /search; Universe filter spans every Series in it	Unit test	GetAll_SeriesFilter_*, GetAll_UniverseFilter_*, GetRandom_*
9-12	✅	Mutual-exclusivity 422, malformed-id 422, unresolved name returns no-results not an error; existing fuzzy filters unaffected	Unit test	QuoteEndpointsTests.GetAll_BothSeriesIdAndSeriesSupplied_*, _MalformedSeriesId_*, _SeriesNameDoesNotResolve_*
13-15	✅	SQL guard coverage; docs updated; no regression	Unit test + Doc	Full suite green
16-17	✅	T1/T2 — live filter/resolution plumbing confirmed against the built image	Live	Confirmed 2026-07-19

This is #196's entity-scoped filter convention's first real consumer. Depended on #206 to give QuoteResponse a clean home for MasterDataReference.