Add per-project card statuses and a kanban board

Statuses
- Migration 006: card_statuses table (project-scoped) and cards.status_id, a
  nullable FK with ON DELETE SET NULL. Every new project is seeded with
  "To do" / "Doing" / "Done"; GET /api/projects/{id}/statuses lists them.
- New cards have no status -- they sit in an "inbox" until moved.

Project view
- Full-width and tabbed: "All tasks" (a flat list, sorted by name
  case-insensitively) and "Kanban" (Inbox plus one column per status).
- Drag a card within or between columns to reorder / restatus; the Inbox
  column has its own name + Add form.

Ordering
- Migration 007: `position` is now a dense 0..n-1 rank within a
  (project_id, status_id) column, not a project-wide order. New composite
  index idx_cards_project_status_position; existing rows re-ranked.
- PUT /api/projects/{id}/cards/order takes { status_id, card_ids } and sets one
  column's contents and order, re-parenting moved-in cards and re-packing their
  source column in a single transaction. PATCH status_id appends the card to the
  end of the destination column.

58 phpunit tests pass; the frontend type-checks and builds.

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

migrations/006_add_card_statuses.sql

@@ -0,0 +1,32 @@
+-- Project-specific card statuses. Every project gets a "To do" / "Doing" /
+-- "Done" set when it is created (see CardStatusRepository::seedDefaults); the
+-- backfill below covers projects that already existed.
+CREATE TABLE IF NOT EXISTS card_statuses (
+    id         INTEGER PRIMARY KEY AUTOINCREMENT,
+    project_id INTEGER NOT NULL REFERENCES projects (id) ON DELETE CASCADE,
+    name       TEXT NOT NULL,
+    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_card_statuses_project_position
+    ON card_statuses (project_id, position);
+
+-- Nullable, and left NULL for existing cards: a card without a status sits in
+-- the project "inbox" until the user gives it one. Losing a status (a deleted
+-- status row) clears the link rather than removing the card.
+ALTER TABLE cards
+    ADD COLUMN status_id INTEGER REFERENCES card_statuses (id) ON DELETE SET NULL;
+
+CREATE INDEX IF NOT EXISTS idx_cards_status ON cards (status_id);
+
+-- Backfill: give every pre-existing project the default status set.
+INSERT INTO card_statuses (project_id, name, position)
+SELECT p.id, d.name, d.position
+FROM projects p
+CROSS JOIN (
+             SELECT 'To do' AS name, 0 AS position
+    UNION ALL SELECT 'Doing',        1
+    UNION ALL SELECT 'Done',         2
+) d;