Merge "custom themes" and "configured/imported CSS" into one mechanism (ticket 012)

The backend already stored both under one CssEntry list (Imported/Linked,
differing only by the is_theme flag), but the NavMenu Settings panel split
them into two visually-duplicated sections — "Custom themes" with its own
upload/link forms and list, and "Import CSS"/"Configured CSS" with a nearly
identical upload form and a separate list — and useSettingsPanel exposed
parallel importCssEntry/importThemeEntry and (theme-only) linkThemeEntry
wrappers around the same underlying API calls.

Consolidate to one "CSS" section: a single list of all CssEntries (each
tagged "theme" and selectable when is_theme is set), one import form and
one link form, each with a "Use as theme" checkbox instead of a duplicate
theme-only form. useSettingsPanel now exposes a single importCssEntry(name,
content, isTheme) and a generic linkCssEntry(url, isTheme) — the latter also
fixes the prior asymmetry where linking (vs. uploading) was only available
for themes, not arbitrary CSS.

No backend or settings-schema changes were needed: is_theme already
persists correctly, so existing custom-theme and imported-CSS
configuration keeps working unmodified under the unified UI.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XFUNZwCvz3kcod3352ZR2o

webapp/src/lib/useSettingsPanel.ts

@@ -162,28 +162,22 @@ export function useSettingsPanel() {
     [guarded],
   )
 
+  // One entry point for both "configured/imported CSS" and "custom themes" —
+  // `isTheme` is the only thing distinguishing them (ticket 012), so there's
+  // no separate theme-only import path.
   const importCssEntry = useCallback(
-    (filename: string, content: string) =>
+    (filename: string, content: string, isTheme = false) =>
       guarded(async () => {
-        await importCss(filename, content)
+        await importCss(filename, content, isTheme)
         await refreshCss()
       })(),
     [guarded, refreshCss],
   )
 
-  const importThemeEntry = useCallback(
-    (filename: string, content: string) =>
+  const linkCssEntry = useCallback(
+    (pathOrUrl: string, isTheme = false) =>
       guarded(async () => {
-        await importCss(filename, content, true)
-        await refreshCss()
-      })(),
-    [guarded, refreshCss],
-  )
-
-  const linkThemeEntry = useCallback(
-    (pathOrUrl: string) =>
-      guarded(async () => {
-        await linkCss(pathOrUrl, true)
+        await linkCss(pathOrUrl, isTheme)
         await refreshCss()
       })(),
     [guarded, refreshCss],
@@ -241,8 +235,7 @@ export function useSettingsPanel() {
     setMaxLogs,
     setNtfySink,
     importCssEntry,
-    importThemeEntry,
-    linkThemeEntry,
+    linkCssEntry,
     removeCssEntry,
     addProfile,
     removeProfile,