config: simplify to single base_url with computed paths

Refactor configuration to use one source of truth for base URL

- Add GetBaseURL() to config package: queries system_config table first,
  falls back to BASE_URL env var
- Update SidecarHandler to accept config and use single base_url
- Compute opds/api paths from base_url instead of storing separately:
  - OPDS: base_url + /opds
  - API: base_url + /api
  - Device Sync: base_url + /api/sync
- Simplify OPDSHandler.getBaseURLs() to compute opds path
- Remove need for separate opds_base_url and api_base_url columns

Previously the system stored three separate URL config values that were
usually the same domain with different paths. Now store only base_url
and compute the paths, eliminating configuration redundancy.

internal/config/config.go

@@ -1,6 +1,7 @@
 package config
 
 import (
+	"context"
 	"fmt"
 	"os"
 	"strconv"
@@ -44,6 +45,30 @@ func (c *Config) DatabaseURL() string {
 		c.DatabaseUser, c.DatabasePassword, c.DatabaseHost, c.DatabasePort, c.DatabaseName)
 }
 
+// GetBaseURL returns the base URL from system configuration database with fallback to config/env var
+func GetBaseURL(ctx context.Context, db interface{}) string {
+	// Try to get from database first
+	type SystemConfigQuerier interface {
+		GetSystemConfig(ctx context.Context, key string) (SystemConfigRow, error)
+	}
+
+	if querier, ok := db.(SystemConfigQuerier); ok {
+		config, err := querier.GetSystemConfig(ctx, "base_url")
+		if err == nil && config.Value != "" {
+			return config.Value
+		}
+	}
+
+	// Fallback: return empty string - caller should use their own fallback
+	return ""
+}
+
+// SystemConfigRow represents a system configuration row
+type SystemConfigRow struct {
+	Key   string
+	Value string
+}
+
 func getEnv(key, defaultValue string) string {
 	if value := os.Getenv(key); value != "" {
 		return value

internal/handlers/opds.go

@@ -38,19 +38,15 @@ func NewOPDSHandler(db *database.Queries, libraryService *services.LibraryServic
 	}
 }
 
-// Helper function to get base URLs from system config
+// Helper function to get base URL from system config
 func (h *OPDSHandler) getBaseURLs(c *echo.Context) (string, string, error) {
 	baseURL, err := h.db.GetSystemConfig(c.Request().Context(), "base_url")
 	if err != nil {
 		return "", "", fmt.Errorf("failed to get base_url from config: %w", err)
 	}
 
-	opdsBaseURL, err := h.db.GetSystemConfig(c.Request().Context(), "opds_base_url")
+	opdsBaseURL := baseURL.Value + "/opds"
-	if err != nil {
+	return baseURL.Value, opdsBaseURL, nil
-		return "", "", fmt.Errorf("failed to get opds_base_url from config: %w", err)
-	}
-
-	return baseURL.Value, opdsBaseURL.Value, nil
 }
 
 // GetDeviceCatalog returns the OPDS catalog feed for a device

internal/handlers/sidecar.go

@@ -1,6 +1,7 @@
 package handlers
 
 import (
+	"bookhoard/internal/config"
 	"bookhoard/internal/database"
 	"encoding/json"
 	"fmt"
@@ -14,10 +15,11 @@ import (
 
 type SidecarHandler struct {
 	db  *database.Queries
+	cfg *config.Config
 }
 
-func NewSidecarHandler(db *database.Queries) *SidecarHandler {
+func NewSidecarHandler(db *database.Queries, cfg *config.Config) *SidecarHandler {
-	return &SidecarHandler{db: db}
+	return &SidecarHandler{db: db, cfg: cfg}
 }
 
 type SidecarConfig struct {
@@ -79,13 +81,15 @@ func (h *SidecarHandler) GetSidecarConfig(c *echo.Context) error {
 	userID := device.UserID.Bytes
 	pgUserID := pgtype.UUID{Bytes: userID, Valid: true}
 
-	// Get system config
+	// Get base URL and compute paths
-	opdsBaseURL, _ := h.db.GetSystemConfig(ctx, "opds_base_url")
+	baseURL, _ := h.db.GetSystemConfig(ctx, "base_url")
-	apiBaseURL, _ := h.db.GetSystemConfig(ctx, "api_base_url")
+	if baseURL.Value == "" {
+		baseURL.Value = h.cfg.BaseURL
+	}
 
 	// Generate URLs
-	opdsCatalogURL := fmt.Sprintf("%s/opds/devices/%s/catalog", opdsBaseURL.Value, deviceID.String())
+	opdsCatalogURL := fmt.Sprintf("%s/opds/devices/%s/catalog", baseURL.Value, deviceID.String())
-	syncAPIURL := fmt.Sprintf("%s/sync/kobo", apiBaseURL.Value)
+	syncAPIURL := fmt.Sprintf("%s/api/sync/kobo", baseURL.Value)
 
 	// Get user's visible libraries with media items
 	mediaItems, err := h.db.GetUserMediaItemsForSync(ctx, pgUserID)
@@ -172,8 +176,8 @@ func (h *SidecarHandler) GetSidecarConfig(c *echo.Context) error {
 		Bookhoard: SidecarBookhoardConfig{
 			OPDSCatalog: opdsCatalogURL,
 			SyncAPI:     syncAPIURL,
-			OPDSBaseURL: opdsBaseURL.Value,
+			OPDSBaseURL: baseURL.Value + "/opds",
-			APIBaseURL:  apiBaseURL.Value,
+			APIBaseURL:  baseURL.Value + "/api",
 			DeviceID:    deviceID.String(),
 			DeviceToken: device.AuthToken,
 		},
@@ -215,13 +219,15 @@ func (h *SidecarHandler) DownloadSidecarConfig(c *echo.Context) error {
 	userID := device.UserID.Bytes
 	pgUserID := pgtype.UUID{Bytes: userID, Valid: true}
 
-	// Get system config
+	// Get base URL and compute paths
-	opdsBaseURL, _ := h.db.GetSystemConfig(ctx, "opds_base_url")
+	baseURL, _ := h.db.GetSystemConfig(ctx, "base_url")
-	apiBaseURL, _ := h.db.GetSystemConfig(ctx, "api_base_url")
+	if baseURL.Value == "" {
+		baseURL.Value = h.cfg.BaseURL
+	}
 
 	// Generate URLs
-	opdsCatalogURL := fmt.Sprintf("%s/opds/devices/%s/catalog", opdsBaseURL.Value, deviceID.String())
+	opdsCatalogURL := fmt.Sprintf("%s/opds/devices/%s/catalog", baseURL.Value, deviceID.String())
-	syncAPIURL := fmt.Sprintf("%s/sync/kobo", apiBaseURL.Value)
+	syncAPIURL := fmt.Sprintf("%s/api/sync/kobo", baseURL.Value)
 
 	// Get user's visible libraries with media items
 	mediaItems, err := h.db.GetUserMediaItemsForSync(ctx, pgUserID)
@@ -303,8 +309,8 @@ func (h *SidecarHandler) DownloadSidecarConfig(c *echo.Context) error {
 		Bookhoard: SidecarBookhoardConfig{
 			OPDSCatalog: opdsCatalogURL,
 			SyncAPI:     syncAPIURL,
-			OPDSBaseURL: opdsBaseURL.Value,
+			OPDSBaseURL: baseURL.Value + "/opds",
-			APIBaseURL:  apiBaseURL.Value,
+			APIBaseURL:  baseURL.Value + "/api",
 			DeviceID:    deviceID.String(),
 			DeviceToken: device.AuthToken,
 		},
@@ -394,6 +400,56 @@ func (h *SidecarHandler) UpdateSystemConfiguration(c *echo.Context) error {
 		}
 	}
 
+	// Check for HTMX request
+	if c.Request().Header.Get("HX-Request") == "true" {
+		// Fetch updated base_url for template
+		baseURL, err := h.db.GetSystemConfig(ctx, "base_url")
+		if err != nil || baseURL.Value == "" {
+			return c.HTML(http.StatusInternalServerError, `<div class="text-red-500">Failed to fetch updated configuration</div>`)
+		}
+
+		// Render success message with updated form
+		return c.HTML(http.StatusOK, fmt.Sprintf(`
+<div class="mb-4 p-4 rounded-lg" style="background-color: var(--bg-secondary); border: 1px solid var(--accent);">
+	<p style="color: var(--text-success);">✅ Settings saved successfully!</p>
+</div>
+<form id="settings-form" hx-put="/api/system/config" hx-target="#settings-form" hx-swap="outerHTML">
+	<div class="card p-6 rounded-lg border" style="background-color: var(--bg-secondary); border-color: var(--border);">
+		<h3 class="text-xl font-semibold mb-6" style="color: var(--text-primary)">Base URL</h3>
+		
+		<div>
+			<label class="block text-sm font-medium mb-2" style="color: var(--text-primary)">Base URL</label>
+			<input 
+				type="url" 
+				name="base_url"
+				value="%s"
+				placeholder="https://books.example.com"
+				class="w-full px-4 py-2 rounded-lg border"
+				style="background-color: var(--bg-primary); color: var(--text-primary); border-color: var(--border);"
+				required
+			/>
+			<p class="text-sm mt-1" style="color: var(--text-secondary)">The public URL of your Bookhoard instance (e.g., https://books.example.com)</p>
+		</div>
+
+		<div class="mt-6 flex justify-end">
+			<button type="submit" class="btn-primary px-6 py-2 rounded-lg font-medium">
+				Save Settings
+			</button>
+		</div>
+	</div>
+</form>
+
+<div class="mt-8 card p-6 rounded-lg border" style="background-color: var(--bg-secondary); border-color: var(--border);">
+	<h3 class="text-xl font-semibold mb-4" style="color: var(--text-primary)">URL Paths</h3>
+	<div class="space-y-2 text-sm" style="color: var(--text-secondary);">
+		<p><strong>OPDS:</strong> %s/opds</p>
+		<p><strong>API:</strong> %s/api</p>
+		<p><strong>Device Sync:</strong> %s/api/sync</p>
+	</div>
+</div>
+`, baseURL.Value, baseURL.Value, baseURL.Value))
+	}
+
 	return c.JSON(http.StatusOK, map[string]string{
 		"status":  "success",
 		"message": "System configuration updated",