Implement user authentication and role-based access control

Three-tier user model: admin (all accounts, all actions), editor
(assigned accounts, read/write), viewer (assigned accounts, read-only).

Backend:
- express-session with custom SQLite session store (no extra packages)
- bcryptjs for password hashing
- src/middleware/auth.js: requireAuth, requireAdmin, requireEditor,
  canAccessAccount helpers
- src/routes/auth.js: login, logout, /me, setup-needed, change-password
- src/routes/users.js: full CRUD + account assignments (admin only)
- All API routes protected; /api/accounts filtered by user access;
  write routes gated by requireEditor; admin-only routes locked down

Frontend:
- Login overlay (full-page) with first-run admin-setup flow
- Role-based UI: admin-only elements hidden for non-admins; edit/delete
  and PDF buttons hidden for viewers; account switcher shows only
  accessible accounts for non-admins
- Users modal (admin only): user list with role badges, create/edit/delete
  users, set account access via checkboxes
- Change-password section available to all logged-in users
- apiFetch redirects to login on 401

package-lock.json

@@ -8,8 +8,10 @@
       "name": "ezcheck",
       "version": "0.1.0",
       "dependencies": {
+        "bcryptjs": "^3.0.3",
         "better-sqlite3": "^9.4.3",
         "express": "^4.18.3",
+        "express-session": "^1.19.0",
         "multer": "^2.1.1",
         "pdfkit": "^0.15.0"
       },
@@ -129,6 +131,15 @@
       ],
       "license": "MIT"
     },
+    "node_modules/bcryptjs": {
+      "version": "3.0.3",
+      "resolved": "https://registry.npmjs.org/bcryptjs/-/bcryptjs-3.0.3.tgz",
+      "integrity": "sha512-GlF5wPWnSa/X5LKM1o0wz0suXIINz1iHRLvTS+sLyi7XPbe5ycmYI3DlZqVGZZtDgl4DmasFg7gOB3JYbphV5g==",
+      "license": "BSD-3-Clause",
+      "bin": {
+        "bcrypt": "bin/bcrypt"
+      }
+    },
     "node_modules/better-sqlite3": {
       "version": "9.6.0",
       "resolved": "https://registry.npmjs.org/better-sqlite3/-/better-sqlite3-9.6.0.tgz",
@@ -717,6 +728,29 @@
         "url": "https://opencollective.com/express"
       }
     },
+    "node_modules/express-session": {
+      "version": "1.19.0",
+      "resolved": "https://registry.npmjs.org/express-session/-/express-session-1.19.0.tgz",
+      "integrity": "sha512-0csaMkGq+vaiZTmSMMGkfdCOabYv192VbytFypcvI0MANrp+4i/7yEkJ0sbAEhycQjntaKGzYfjfXQyVb7BHMA==",
+      "license": "MIT",
+      "dependencies": {
+        "cookie": "~0.7.2",
+        "cookie-signature": "~1.0.7",
+        "debug": "~2.6.9",
+        "depd": "~2.0.0",
+        "on-headers": "~1.1.0",
+        "parseurl": "~1.3.3",
+        "safe-buffer": "~5.2.1",
+        "uid-safe": "~2.1.5"
+      },
+      "engines": {
+        "node": ">= 0.8.0"
+      },
+      "funding": {
+        "type": "opencollective",
+        "url": "https://opencollective.com/express"
+      }
+    },
     "node_modules/file-uri-to-path": {
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/file-uri-to-path/-/file-uri-to-path-1.0.0.tgz",
@@ -1679,6 +1713,15 @@
         "node": ">= 0.8"
       }
     },
+    "node_modules/on-headers": {
+      "version": "1.1.0",
+      "resolved": "https://registry.npmjs.org/on-headers/-/on-headers-1.1.0.tgz",
+      "integrity": "sha512-737ZY3yNnXy37FHkQxPzt4UZ2UWPWiCZWLvFZ4fu5cueciegX0zGPnrlY6bwRg4FdQOe9YU8MkmJwGhoMybl8A==",
+      "license": "MIT",
+      "engines": {
+        "node": ">= 0.8"
+      }
+    },
     "node_modules/once": {
       "version": "1.4.0",
       "resolved": "https://registry.npmjs.org/once/-/once-1.4.0.tgz",
@@ -1821,6 +1864,15 @@
         "url": "https://github.com/sponsors/ljharb"
       }
     },
+    "node_modules/random-bytes": {
+      "version": "1.0.0",
+      "resolved": "https://registry.npmjs.org/random-bytes/-/random-bytes-1.0.0.tgz",
+      "integrity": "sha512-iv7LhNVO047HzYR3InF6pUcUsPQiHTM1Qal51DcGSuZFBil1aBBWG5eHPNek7bvILMaYJ/8RU1e8w1AMdHmLQQ==",
+      "license": "MIT",
+      "engines": {
+        "node": ">= 0.8"
+      }
+    },
     "node_modules/range-parser": {
       "version": "1.2.1",
       "resolved": "https://registry.npmjs.org/range-parser/-/range-parser-1.2.1.tgz",
@@ -2345,6 +2397,18 @@
       "integrity": "sha512-/aCDEGatGvZ2BIk+HmLf4ifCJFwvKFNb9/JeZPMulfgFracn9QFcAf5GO8B/mweUjSoblS5In0cWhqpfs/5PQA==",
       "license": "MIT"
     },
+    "node_modules/uid-safe": {
+      "version": "2.1.5",
+      "resolved": "https://registry.npmjs.org/uid-safe/-/uid-safe-2.1.5.tgz",
+      "integrity": "sha512-KPHm4VL5dDXKz01UuEd88Df+KzynaohSL9fBh096KWAxSKZQDI2uBrVqtvRM4rwrIrRRKsdLNML/lnaaVSRioA==",
+      "license": "MIT",
+      "dependencies": {
+        "random-bytes": "~1.0.0"
+      },
+      "engines": {
+        "node": ">= 0.8"
+      }
+    },
     "node_modules/undefsafe": {
       "version": "2.0.5",
       "resolved": "https://registry.npmjs.org/undefsafe/-/undefsafe-2.0.5.tgz",