feat: frontend MVP — auth, timeline, upload, albums, admin, image viewer

Backend:
- user roles (DB + JWT + first-user-is-admin)
- volume-aware file resolver (multi-volume asset serving)
- directory scanner uses volume URI directly
- date-summary endpoint (capture date from EXIF)
- timeline ordered by capture date
- list endpoints: volumes, plugins, pipelines, library paths
- delete endpoints: volumes, library paths
- configurable upload body limit (MAX_UPLOAD_BYTES)

Frontend:
- auth: login/register, token refresh, role-based admin gate
- timeline: date-grouped grid, infinite scroll, date scrubber
- image viewer: fullscreen zoom/pan/pinch, metadata sidebar
- upload: drag-drop, sequential upload, progress tracking
- albums: create, add/remove photos, asset picker dialog
- admin: storage (import library), jobs (pagination, error details),
  plugins (list + toggle), pipelines, sidecars, duplicates
- multi-select mode with add-to-album action
- TanStack Query for all data fetching

k-photos-frontend/components/auth-provider.tsx

@@ -0,0 +1,81 @@
+"use client"
+
+import { createContext, useState, useEffect, useCallback, type ReactNode } from "react"
+import api from "@/lib/api"
+import { getTokens, setTokens, clearTokens } from "@/lib/auth"
+import type { AuthResponse, UserResponse } from "@/lib/types"
+
+interface AuthContextValue {
+  user: UserResponse | null
+  isAuthenticated: boolean
+  isAdmin: boolean
+  isLoading: boolean
+  login: (email: string, password: string) => Promise<void>
+  register: (username: string, email: string, password: string) => Promise<void>
+  logout: () => void
+}
+
+export const AuthContext = createContext<AuthContextValue | null>(null)
+
+export function AuthProvider({ children }: { children: ReactNode }) {
+  const [user, setUser] = useState<UserResponse | null>(null)
+  const [isLoading, setIsLoading] = useState(true)
+
+  useEffect(() => {
+    const { access } = getTokens()
+    if (!access) {
+      setIsLoading(false)
+      return
+    }
+    api
+      .get<UserResponse>("/auth/me")
+      .then((res) => setUser(res.data))
+      .catch(() => clearTokens())
+      .finally(() => setIsLoading(false))
+  }, [])
+
+  const login = useCallback(async (email: string, password: string) => {
+    const { data } = await api.post<AuthResponse>("/auth/login", {
+      email,
+      password,
+    })
+    setTokens(data.token, data.refresh_token)
+    setUser(data.user)
+  }, [])
+
+  const register = useCallback(
+    async (username: string, email: string, password: string) => {
+      const { data } = await api.post<AuthResponse>("/auth/register", {
+        username,
+        email,
+        password,
+      })
+      setTokens(data.token, data.refresh_token)
+      setUser(data.user)
+    },
+    [],
+  )
+
+  const logout = useCallback(() => {
+    api.post("/auth/logout").catch(() => {})
+    clearTokens()
+    setUser(null)
+    window.location.href = "/login"
+  }, [])
+
+  return (
+    <AuthContext.Provider
+      value={{
+        user,
+        isAuthenticated: !!user,
+        isAdmin: user?.role === "admin",
+        isLoading,
+        login,
+        register,
+        logout,
+      }}
+    >
+      {children}
+    </AuthContext.Provider>
+  )
+}