schema: add composite index (is_published, year DESC) + fix stale migration 005

- Add idx_theses_pub_year composite index on theses(is_published, year DESC) to
  schema.sql; replaces the need for the query planner to pick between the two
  separate idx_theses_published / idx_theses_year indexes and sort with a temp
  B-tree. Every public query filters on is_published=1 and orders/filters by year,
  so this covering index eliminates the sort pass for those queries.

- Create storage/migrations/006_add_composite_index.sql and apply to both
  posterg.db and test.db.

- Fix storage/migrations/005_add_banner.sql: the view recreation in that file
  still referenced the pre-migration-001 table/column names (thesis_keywords,
  keywords.keyword). Updated to use thesis_tags / tags tg to match the canonical
  schema.sql. The live DB was unaffected (migration 001 ran before 005), but the
  file was misleading and would fail if ever re-run from scratch.

TODO.md

@@ -351,7 +351,7 @@ Goal: rename the tables and column to the canonical M2M pattern (`tags`, `thesis
       Eliminates full-database read-locks on every write; makes concurrent PHP-FPM workers safe.
       Also add `PRAGMA cache_size = -8000` (≈8 MB page cache) while there.
 
-- [ ] **Composite index `(is_published, year DESC)`** on `theses` — every public query filters on both.
+- [x] **Composite index `(is_published, year DESC)`** on `theses` — every public query filters on both.
       Currently `idx_theses_published` and `idx_theses_year` are separate; the query planner picks one
       and sorts the other with a temp B-tree. A single covering index eliminates the sort:
       `CREATE INDEX IF NOT EXISTS idx_theses_pub_year ON theses(is_published, year DESC);`
@@ -370,7 +370,7 @@ Goal: rename the tables and column to the canonical M2M pattern (`tags`, `thesis
       `Database::getPublishedAuthors(): array` that queries `thesis_authors JOIN authors` directly,
       avoiding the view entirely.
 
-- [ ] **`migration 005` view is stale in the file** — `005_add_banner.sql` recreates the view still
+- [x] **`migration 005` view is stale in the file** — `005_add_banner.sql` recreates the view still
       referencing `thesis_keywords` / `keywords.keyword` (the old pre-migration-001 names).
       The file is already applied to the live DB (correctly, since 001 ran first), but the migration
       file itself is wrong and misleading. Fix: rewrite it to reference `thesis_tags` / `tags.name`,

storage/migrations/005_add_banner.sql

@@ -38,7 +38,7 @@ SELECT
     GROUP_CONCAT(DISTINCT CASE WHEN ts.role = 'lecteur'    THEN s.name END) as jury_lecteurs,
     GROUP_CONCAT(DISTINCT l.name) as languages,
     GROUP_CONCAT(DISTINCT fmt.name) as formats,
-    GROUP_CONCAT(DISTINCT k.keyword) as keywords
+    GROUP_CONCAT(DISTINCT tg.name) as keywords
 FROM theses t
 LEFT JOIN orientations o ON t.orientation_id = o.id
 LEFT JOIN ap_programs ap ON t.ap_program_id = ap.id
@@ -53,8 +53,8 @@ LEFT JOIN thesis_languages tl ON t.id = tl.thesis_id
 LEFT JOIN languages l ON tl.language_id = l.id
 LEFT JOIN thesis_formats tf ON t.id = tf.thesis_id
 LEFT JOIN format_types fmt ON tf.format_id = fmt.id
-LEFT JOIN thesis_keywords tk ON t.id = tk.thesis_id
+LEFT JOIN thesis_tags tt ON t.id = tt.thesis_id
-LEFT JOIN keywords k ON tk.keyword_id = k.id
+LEFT JOIN tags tg ON tt.tag_id = tg.id
 GROUP BY t.id;
 
 -- Recreate public view

storage/migrations/006_add_composite_index.sql

@@ -0,0 +1,8 @@
+-- Migration 006: Add composite covering index (is_published, year DESC) on theses
+--
+-- Every public-facing query filters on is_published = 1 AND orders/filters by year.
+-- The existing separate idx_theses_published and idx_theses_year force the query
+-- planner to pick one index and sort the other via a temp B-tree.
+-- This single covering index eliminates the extra sort pass.
+
+CREATE INDEX IF NOT EXISTS idx_theses_pub_year ON theses(is_published, year DESC);

storage/schema.sql

@@ -306,6 +306,7 @@ INSERT OR IGNORE INTO pages (slug, title, content) VALUES
 
 CREATE INDEX IF NOT EXISTS idx_theses_year ON theses(year);
 CREATE INDEX IF NOT EXISTS idx_theses_published ON theses(is_published);
+CREATE INDEX IF NOT EXISTS idx_theses_pub_year ON theses(is_published, year DESC);
 CREATE INDEX IF NOT EXISTS idx_theses_identifier ON theses(identifier);
 CREATE INDEX IF NOT EXISTS idx_theses_orientation ON theses(orientation_id);
 CREATE INDEX IF NOT EXISTS idx_theses_ap_program ON theses(ap_program_id);