refactor: rename keywords→tags M2M (migration 001)

- migration 001_rename_keywords_to_tags.sql: CREATE tags/thesis_tags from keywords/thesis_keywords,
  copy data, drop old tables, rebuild indexes and views
- schema.sql: tags table, thesis_tags junction, updated indexes and v_theses_full/v_theses_public
- Database.php: findOrCreateTag(), getUsedTags() with proper JOIN; backwards-compat aliases;
  buildSearchConditions uses EXISTS subquery on thesis_tags+tags with vp. alias throughout
- admin/actions/formulaire.php: INSERT OR IGNORE INTO thesis_tags
- admin/edit.php: DELETE FROM thesis_tags + findOrCreateTag
- search.php: $kw['name'] (was $kw['keyword'])
- fixtures/CreateTestDatabase.php: tags/thesis_tags table names

storage/migrations/001_rename_keywords_to_tags.sql

@@ -0,0 +1,106 @@
+-- Migration 001: Rename keywords→tags, thesis_keywords→thesis_tags, keyword column→name
+-- SQLite does not support ALTER TABLE RENAME COLUMN before 3.25, so we recreate tables.
+-- This migration is safe to run after 004 and 005 (no dependency ordering required
+-- since SQLite processes this in one transaction).
+
+PRAGMA foreign_keys = OFF;
+
+BEGIN;
+
+-- 1. Create new tags table
+CREATE TABLE tags (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    name TEXT NOT NULL UNIQUE,
+    created_at DATETIME DEFAULT CURRENT_TIMESTAMP
+);
+
+-- 2. Copy data from keywords → tags (keyword column → name)
+INSERT INTO tags (id, name, created_at)
+SELECT id, keyword, created_at FROM keywords;
+
+-- 3. Create new junction table thesis_tags
+CREATE TABLE thesis_tags (
+    tag_id INTEGER NOT NULL,
+    thesis_id INTEGER NOT NULL,
+    PRIMARY KEY (tag_id, thesis_id),
+    FOREIGN KEY (thesis_id) REFERENCES theses(id) ON DELETE CASCADE,
+    FOREIGN KEY (tag_id) REFERENCES tags(id) ON DELETE CASCADE
+);
+
+-- 4. Copy junction data (keyword_id → tag_id)
+INSERT INTO thesis_tags (tag_id, thesis_id)
+SELECT keyword_id, thesis_id FROM thesis_keywords;
+
+-- 5. Drop old tables
+DROP TABLE thesis_keywords;
+DROP TABLE keywords;
+
+-- 6. Recreate indexes with canonical names
+CREATE INDEX idx_tags_name ON tags(name);
+CREATE INDEX idx_thesis_tags_thesis ON thesis_tags(thesis_id);
+CREATE INDEX idx_thesis_tags_tag    ON thesis_tags(tag_id);
+
+-- 7. Rebuild views to reference new tables
+DROP VIEW IF EXISTS v_theses_full;
+
+CREATE VIEW v_theses_full AS
+SELECT
+    t.id,
+    t.identifier,
+    t.title,
+    t.subtitle,
+    t.year,
+    t.is_doctoral,
+    o.name as orientation,
+    ap.name as ap_program,
+    ft.name as finality_type,
+    t.synopsis,
+    t.context_note,
+    t.duration_minutes,
+    t.duration_pages,
+    t.file_size_info,
+    at.name as access_type,
+    lt.name as license_type,
+    t.license_id,
+    t.jury_points,
+    t.submitted_at,
+    t.defense_date,
+    t.published_at,
+    t.is_published,
+    t.baiu_link,
+    t.banner_path,
+    GROUP_CONCAT(DISTINCT a.name) as authors,
+    GROUP_CONCAT(DISTINCT s.name) as supervisors,
+    GROUP_CONCAT(DISTINCT CASE WHEN ts.role = 'president' THEN s.name END) as jury_president,
+    GROUP_CONCAT(DISTINCT CASE WHEN ts.role = 'promoteur' THEN s.name END) as jury_promoteurs,
+    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 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
+LEFT JOIN finality_types ft ON t.finality_id = ft.id
+LEFT JOIN access_types at ON t.access_type_id = at.id
+LEFT JOIN license_types lt ON t.license_id = lt.id
+LEFT JOIN thesis_authors ta ON t.id = ta.thesis_id
+LEFT JOIN authors a ON ta.author_id = a.id
+LEFT JOIN thesis_supervisors ts ON t.id = ts.thesis_id
+LEFT JOIN supervisors s ON ts.supervisor_id = s.id
+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_tags tt ON t.id = tt.thesis_id
+LEFT JOIN tags tg ON tt.tag_id = tg.id
+GROUP BY t.id;
+
+DROP VIEW IF EXISTS v_theses_public;
+
+CREATE VIEW v_theses_public AS
+SELECT * FROM v_theses_full
+WHERE is_published = 1;
+
+COMMIT;
+
+PRAGMA foreign_keys = ON;