feat: Add Cantaloupe sync API with staged import workflow

- New cantaloupe_sync.py module with complete pipeline
- Heuristic Excel column mapping (20+ keyword patterns)
- Diff engine: detects new/changed/removed/unchanged assets
- 5 API endpoints: sync, list batches, view batch, approve, reject
- cantaloupe_sync_batches table with status workflow
- Admin server port changed to 8090
- openpyxl added to requirements.txt

admin_server.py

@@ -26,6 +26,8 @@ from fastapi.middleware.cors import CORSMiddleware
 from fastapi.responses import JSONResponse, StreamingResponse
 from pydantic import BaseModel
 
+from cantaloupe_sync import router as cantaloupe_router, create_sync_tables
+
 # ─── Config ─────────────────────────────────────────────────────────────────
 
 VALID_CATEGORIES = {"Furniture", "Appliances", "Utensils & Serveware", "Equipment", "Other"}
@@ -241,10 +243,24 @@ def _create_tables(conn: sqlite3.Connection):
             created_at  TEXT    NOT NULL DEFAULT (datetime('now'))
         );
 
+        CREATE TABLE IF NOT EXISTS cantaloupe_sync_batches (
+            id              INTEGER PRIMARY KEY AUTOINCREMENT,
+            status          TEXT    NOT NULL DEFAULT 'pending',
+            created_at      TEXT    NOT NULL DEFAULT (datetime('now')),
+            approved_at     TEXT,
+            file_path       TEXT,
+            row_count       INTEGER DEFAULT 0,
+            diff_summary    TEXT,
+            raw_data        TEXT,
+            error_message   TEXT
+        );
+
         CREATE INDEX IF NOT EXISTS idx_checkins_asset_id ON checkins(asset_id);
         CREATE INDEX IF NOT EXISTS idx_checkins_created_at ON checkins(created_at);
         CREATE INDEX IF NOT EXISTS idx_assets_category ON assets(category);
         CREATE INDEX IF NOT EXISTS idx_assets_machine_id ON assets(machine_id);
+        CREATE INDEX IF NOT EXISTS idx_csb_status ON cantaloupe_sync_batches(status);
+        CREATE INDEX IF NOT EXISTS idx_csb_created ON cantaloupe_sync_batches(created_at);
     """)
 
 
@@ -293,6 +309,7 @@ def _seed_data(conn: sqlite3.Connection):
 def init_db(conn: sqlite3.Connection):
     """Ensure all tables exist, run migrations if needed, seed default data."""
     _create_tables(conn)
+    create_sync_tables(conn)
     _seed_data(conn)
     # Add lat/lng columns if missing (v3 migration)
     cursor = conn.execute("PRAGMA table_info(assets)")
@@ -334,6 +351,9 @@ app.add_middleware(
     allow_headers=["*"],
 )
 
+# Mount Cantaloupe sync routes
+app.include_router(cantaloupe_router)
+
 
 # ─── Auth Middleware ────────────────────────────────────────────────────────