Rename lists -> projects and items -> cards throughout

Project scope shifts from a todo list to a project-management app. This is a
straight terminology rename across code, comments, migrations, tests, and
docs — no behaviour change.

- DB: table todo_lists -> projects, todo_items -> cards, column
  todo_items.list_id -> cards.project_id, indexes renamed. Migrations 003/004
  rewritten in place (destructive; recreate the volume with `down -v`).
- API: /api/lists -> /api/projects, nested /items -> /cards, reorder body
  item_ids -> card_ids, JSON keys list/lists/item/items -> project/projects/
  card/cards, item_count -> card_count, list_id -> project_id, and the
  matching error messages.
- PHP: TodoList/TodoItem Repository + Controller -> Project/Card; shared SQL
  aliases l/i -> p/c.
- Frontend: stores lists.ts/items.ts -> projects.ts/cards.ts (useProjectsStore
  / useCardsStore, MAX_PROJECTS), ListView -> ProjectView, TodoItemRow ->
  CardRow, route /lists/:id -> /projects/:id (name "project"), types TodoList/
  TodoItem -> Project/Card, and all UI copy. CSS .lists*/.list-head* ->
  .projects*/.project-head*, .item* -> .card-row* (kept the generic .card
  panel class), .items -> .cards.
- Product name in the header, PWA manifest, index.html title and package
  descriptions -> "Project Manager" / "Projects".

Backend suite: 37 passing.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

migrations/004_create_cards_table.sql

@@ -0,0 +1,11 @@
+CREATE TABLE IF NOT EXISTS cards (
+    id         INTEGER PRIMARY KEY AUTOINCREMENT,
+    project_id INTEGER NOT NULL REFERENCES projects (id) ON DELETE CASCADE,
+    text       TEXT NOT NULL,
+    complete   INTEGER NOT NULL DEFAULT 0 CHECK (complete IN (0, 1)),
+    position   INTEGER NOT NULL DEFAULT 0,
+    created_at TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
+    updated_at TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%SZ', 'now'))
+);
+
+CREATE INDEX IF NOT EXISTS idx_cards_project_position ON cards (project_id, position);