Add GET /collections browse endpoint; fix embedded collection poster_path

Completes browse/discover across all five entity types: movies, series,
people, companies, and now collections. No filter (no categorical field
like company_type exists for a collection) -- just page/page_size,
always alphabetical by name.

While adding poster_path to CollectionBriefOut for the browse listing,
found the same class of bug fixed earlier for company logo_path:
movie_service's embedded `collection` field never looked up its poster
artwork either, so it stayed null even after ingest_collection populated
one. Fixed alongside since it's the same schema field this feature was
already touching.

Also removed PageMeta from schemas/common.py -- scaffolding from early
spec work that was never actually wired into any endpoint; all five
browse endpoints shipped this session use a flat page/page_size/
total_results/total_pages shape instead.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

docs/api.md

@@ -94,7 +94,7 @@ unknown status) is a 422, not a silently-empty result. Response:
   "cast": [{ "id": "aur_credit_...", "person": { "id": "aur_person_...", "name": "Keanu Reeves", "profile_path": null }, "character": "Neo", "billing_order": 0 }],
   "crew": [{ "id": "aur_credit_...", "person": { "id": "aur_person_...", "name": "Lana Wachowski" }, "department": "Directing", "job": "Director" }],
   "companies": [{ "id": "aur_company_...", "name": "Village Roadshow Pictures", "company_type": "production_company" }],
-  "collection": { "id": "aur_collection_...", "name": "The Matrix Collection" },
+  "collection": { "id": "aur_collection_...", "name": "The Matrix Collection", "poster_path": "https://..." },
   "images": { "posters": [...], "backdrops": [...], "logos": [...] },
   "videos": [{ "id": "aur_vid_...", "type": "trailer", "site": "YouTube", "url": "https://www.youtube.com/watch?v=...", "is_official": true }],
   "external_ids": { "tmdb": "603", "imdb": "tt0133093" },
@@ -165,6 +165,7 @@ pagination and response shape as `/movies` and `/series`.
 
 | Method | Path |
 |---|---|
+| GET | `/api/v1/collections` |
 | GET | `/api/v1/collections/{aurora_id}` |
 | GET | `/api/v1/companies` |
 | GET | `/api/v1/companies/{aurora_id}` |
@@ -175,6 +176,12 @@ pagination and response shape as `/movies` and `/series`.
 `page_size` pagination. No `sort_by` — companies have no popularity or
 date field to sort by, so results are always alphabetical by name.
 
+`GET /api/v1/collections` is the same idea for collections/franchises, but
+with no filter at all (no categorical field like `company_type` exists for
+a collection) — just `page`/`page_size`, always alphabetical by name. This
+is the last entity type to get a browse endpoint: movies, series, people,
+companies, and collections are all browsable now.
+
 Collection detail's `movies` list only includes movies already ingested
 into Aurora — `POST /api/v1/admin/ingest/collection` links a franchise's
 member movies purely by external-id lookup, the same never-fabricate-a-stub