test: clarify 1h advance requirement is USER-ONLY, add admin walk-in tests

FIXES:
- Clarified that 1-hour minimum advance requirement applies to USER bookings only
- Admins can create walk-in bookings with no advance notice via AdminCreateBookingForUserHandler
- Updated test comments to reflect this distinction

NEW TESTS ADDED:
- TestAdminBookings_Create_WalkIn: Admin creates booking with < 1h notice (walk-in)
- TestAdminBookings_Create_WalkInWithDeposits: Admin walk-in with outstanding deposits + enforce_deposits=false

TEST SCENARIOS VERIFIED:
✓ User: Cannot book < 1h in advance (400 error)
✓ Admin: CAN book < 1h in advance (walk-in, 201 created)
✓ Admin: Can create walk-ins even with user deposits (with enforce_deposits bypass)
✓ Admin: Can bypass minimum advance requirement

BUILD STATUS:
✓ go build -tags test ./handlers/bookings
✓ go build -tags test ./handlers/admin
✓ go build -tags dev ./main.go

Documentation now clearly distinguishes:
- User journey: 1h minimum advance (universal)
- Admin journey: No minimum advance (accept walk-ins)

obsidian/.obsidian/workspace.json

@@ -4,21 +4,17 @@
     "type": "split",
     "children": [
       {
-        "id": "4f4ac1241ce3420f",
+        "id": "c3304ad1f15b3261",
         "type": "tabs",
         "children": [
           {
-            "id": "0c84336298f72379",
+            "id": "b72bbfe2e0c01c0c",
             "type": "leaf",
             "state": {
-              "type": "markdown",
-              "state": {
-                "file": "Crussell/Crussell Nails.md",
-                "mode": "source",
-                "source": false
-              },
+              "type": "empty",
+              "state": {},
               "icon": "lucide-file",
-              "title": "Crussell Nails"
+              "title": "New tab"
             }
           }
         ]
@@ -74,7 +70,8 @@
               "title": "Bookmarks"
             }
           }
-        ]
+        ],
+        "currentTab": 1
       }
     ],
     "direction": "horizontal",
@@ -169,10 +166,10 @@
       "bases:Create new base": false
     }
   },
-  "active": "0c84336298f72379",
+  "active": "b72bbfe2e0c01c0c",
   "lastOpenFiles": [
-    "Crussell/Backend/bookings.md",
     "Crussell/Crussell Nails.md",
+    "Crussell/Backend/bookings.md",
     "Untitled.base",
     "Untitled.canvas",
     "Express.js Cheat Sheet.md"