feat(v4.5.0): Sprints & My Tasks

- New tables: sprints + sprint_pages with velocity_points
- API: CRUD sprints (list/create/update/delete)
- API: assign/remove pages to sprints
- API: burndown chart data (total/completed/remaining points, ideal line)
- 4 new tests (175 total)

app/db.py

@@ -536,6 +536,32 @@ def init_db():
         """)
         conn.commit()
 
+        # v4.5.0: Sprints
+        conn.execute("""
+            CREATE TABLE IF NOT EXISTS sprints (
+                id INTEGER PRIMARY KEY AUTOINCREMENT,
+                collection_id INTEGER NOT NULL REFERENCES collections(id) ON DELETE CASCADE,
+                name TEXT NOT NULL,
+                start_date TEXT NOT NULL,
+                end_date TEXT NOT NULL,
+                goal TEXT DEFAULT '',
+                status TEXT NOT NULL DEFAULT 'planning',
+                auto_complete BOOLEAN NOT NULL DEFAULT 1,
+                created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+            )
+        """)
+        conn.execute("""
+            CREATE TABLE IF NOT EXISTS sprint_pages (
+                id INTEGER PRIMARY KEY AUTOINCREMENT,
+                sprint_id INTEGER NOT NULL REFERENCES sprints(id) ON DELETE CASCADE,
+                page_id INTEGER NOT NULL REFERENCES collection_pages(id) ON DELETE CASCADE,
+                status_at_start TEXT DEFAULT '',
+                velocity_points INTEGER DEFAULT 1,
+                UNIQUE(sprint_id, page_id)
+            )
+        """)
+        conn.commit()
+
 
 @contextmanager
 def get_conn():