Refactor settings system and improve context initialization

Backend:
- Add type validation and coercion for settings API
- Implement SettingStorage and SettingType in registry
- Improve CRUD operations for settings

Frontend:
- Refactor Theme, Language, Sidebar, ViewMode contexts
- Simplify admin components (GeneralTab, SettingsTab, UsersTab)
- Add new settings endpoints to API client
- Improve App initialization flow

Infrastructure:
- Update Dockerfile and docker-compose.yml
- Add .dockerignore
- Update Makefile and README

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/contexts/SidebarContext.tsx

@@ -1,6 +1,7 @@
 import { createContext, useContext, useState, useEffect, useCallback } from 'react';
 import type { ReactNode } from 'react';
 import { useAuth } from './AuthContext';
+import { settingsAPI } from '../api/client';
 
 export type SidebarMode = 'collapsed' | 'expanded' | 'toggle' | 'dynamic';
 
@@ -23,47 +24,57 @@ const SidebarContext = createContext<SidebarContextType | undefined>(undefined);
 
 export function SidebarProvider({ children }: { children: ReactNode }) {
   const { token } = useAuth();
-  const [userCollapsed, setUserCollapsed] = useState(true);
+  const [userCollapsed, setUserCollapsed] = useState(() => {
+    const key = 'user_sidebar_collapsed';
+    const saved = localStorage.getItem(key);
+    if (saved === 'true') return true;
+    if (saved === 'false') return false;
+
+    // Backward-compatibility: migrate legacy key
+    const legacy = localStorage.getItem('sidebarCollapsed');
+    if (legacy === 'true' || legacy === 'false') {
+      localStorage.setItem(key, legacy);
+      localStorage.removeItem('sidebarCollapsed');
+      return legacy === 'true';
+    }
+
+    return true;
+  });
   const [isMobileOpen, setIsMobileOpen] = useState(false);
   const [sidebarMode, setSidebarModeState] = useState<SidebarMode>('toggle');
   const [isHovered, setIsHovered] = useState(false);
   const [showLogo, setShowLogo] = useState(false);
 
   // Load sidebar mode from backend
-  useEffect(() => {
-    const loadSidebarMode = async () => {
-      try {
-        if (!token) {
-          setSidebarModeState('toggle');
-          setShowLogo(false);
-          return;
-        }
+	  useEffect(() => {
+	    const loadSidebarMode = async () => {
+	      try {
+	        if (!token) {
+	          setSidebarModeState('toggle');
+	          setShowLogo(false);
+	          return;
+	        }
 
-        const response = await fetch('/api/v1/settings/ui', {
-          headers: { 'Authorization': `Bearer ${token}` }
-        });
-        if (response.ok) {
-          const data = await response.json();
-          const parseBool = (val: any, defaultVal: boolean): boolean => {
-            if (val === undefined || val === null) return defaultVal;
-            if (val === true || val === 'true' || val === 'True' || val === 1 || val === '1') return true;
-            if (val === false || val === 'false' || val === 'False' || val === 0 || val === '0') return false;
-            return defaultVal;
-          };
+	        const data = await settingsAPI.getUi();
+	        const parseBool = (val: any, defaultVal: boolean): boolean => {
+	          if (val === undefined || val === null) return defaultVal;
+	          if (val === true || val === 'true' || val === 'True' || val === 1 || val === '1') return true;
+	          if (val === false || val === 'false' || val === 'False' || val === 0 || val === '0') return false;
+	          return defaultVal;
+	        };
 
-          if (data.sidebar_mode && ['collapsed', 'expanded', 'toggle', 'dynamic'].includes(data.sidebar_mode)) {
-            setSidebarModeState(data.sidebar_mode as SidebarMode);
-          }
-          if (data.show_logo !== undefined) {
-            setShowLogo(parseBool(data.show_logo, false));
-          }
-        }
-      } catch (error) {
-        console.error('Failed to load sidebar mode:', error);
-      }
-    };
-    loadSidebarMode();
-  }, [token]);
+	        if (data.sidebar_mode && ['collapsed', 'expanded', 'toggle', 'dynamic'].includes(data.sidebar_mode as string)) {
+	          setSidebarModeState(data.sidebar_mode as SidebarMode);
+	        }
+	        if (data.show_logo !== undefined) {
+	          setShowLogo(parseBool(data.show_logo, false));
+	        }
+	      } catch (error) {
+	        console.error('Failed to load sidebar mode:', error);
+	      }
+	    };
+	    loadSidebarMode();
+	  }, [token]);
 
   // Compute isCollapsed based on mode
   const isCollapsed = sidebarMode === 'collapsed' ? true :
@@ -76,7 +87,11 @@ export function SidebarProvider({ children }: { children: ReactNode }) {
 
   const toggleCollapse = () => {
     if (canToggle) {
-      setUserCollapsed((prev) => !prev);
+      setUserCollapsed((prev) => {
+        const next = !prev;
+        localStorage.setItem('user_sidebar_collapsed', String(next));
+        return next;
+      });
     }
   };
 
@@ -88,25 +103,15 @@ export function SidebarProvider({ children }: { children: ReactNode }) {
     setIsMobileOpen(false);
   };
 
-  const setSidebarMode = useCallback(async (mode: SidebarMode) => {
-    try {
-      if (!token) return;
-      const response = await fetch('/api/v1/settings/sidebar_mode', {
-        method: 'PUT',
-        headers: {
-          'Authorization': `Bearer ${token}`,
-          'Content-Type': 'application/json',
-        },
-        body: JSON.stringify({ value: mode }),
-      });
-
-      if (response.ok) {
-        setSidebarModeState(mode);
-      }
-    } catch (error) {
-      console.error('Failed to save sidebar mode:', error);
-    }
-  }, [token]);
+	  const setSidebarMode = useCallback(async (mode: SidebarMode) => {
+	    try {
+	      if (!token) return;
+	      await settingsAPI.updateSetting('sidebar_mode', mode);
+	      setSidebarModeState(mode);
+	    } catch (error) {
+	      console.error('Failed to save sidebar mode:', error);
+	    }
+	  }, [token]);
 
   return (
     <SidebarContext.Provider