feat(v4.4.0): Tasks, Sub-items & Dependencies

- Add is_task flag on collections (toggle-task API)
- New page_dependencies table with auto_shift config (blocks/blocked_by/related)
- API: GET/POST/DELETE page dependencies
- API: POST auto-shift dates based on blocking dependencies (skip_weekends option)
- 5 new tests (171 total)

app/db.py

@@ -515,6 +515,27 @@ def init_db():
         """)
         conn.commit()
 
+        # v4.4.0: Tasks & Dependencies
+        # Add is_task flag to collections
+        try:
+            conn.execute("ALTER TABLE collections ADD COLUMN is_task BOOLEAN NOT NULL DEFAULT 0")
+        except sqlite3.OperationalError:
+            pass
+
+        # Dependencies table: bloque/bloqué par with auto-shift config
+        conn.execute("""
+            CREATE TABLE IF NOT EXISTS page_dependencies (
+                id INTEGER PRIMARY KEY AUTOINCREMENT,
+                page_id INTEGER NOT NULL REFERENCES collection_pages(id) ON DELETE CASCADE,
+                dependency_id INTEGER NOT NULL REFERENCES collection_pages(id) ON DELETE CASCADE,
+                dependency_type TEXT NOT NULL DEFAULT 'blocks',
+                auto_shift TEXT DEFAULT 'overlap',
+                created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+                UNIQUE(page_id, dependency_id, dependency_type)
+            )
+        """)
+        conn.commit()
+
 
 @contextmanager
 def get_conn():