Albums: name search and sort by name / modification date

The album grid now shows a filtered + sorted view of the list:
- SQUARE (or tap the header pill) opens the keyboard to filter albums
  by name (case-insensitive); O clears the filter before going back.
- SELECT (or tap the chip) cycles the order: modified newest/oldest,
  name A-Z/Z-A. Uses the album's updatedAt from GET /api/albums.
- Cover eviction no longer drops a texture that a visible card still
  uses when two albums share the same cover photo.
- README: albums controls.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/state.c

@@ -140,11 +140,13 @@ static char (*g_album_thumb)[40];   /* cover asset id, "" when none */
 static int *g_album_nassets;        /* assetCount reported by the server */
 static unsigned char *g_album_shared;   /* shared with other users */
 static unsigned char *g_album_has_link;  /* has a public share link */
+static char (*g_album_updated)[32]; /* updatedAt (ISO 8601, sorts as text) */
 static int g_album_len;             /* number of albums fetched */
 static int g_album_cap;
 
 static int g_album_state;
 static volatile int g_album_fetching;
+static volatile int g_album_list_dirty; /* list (re)fetched: rebuild the view */
 
 static int g_album_active;          /* grid is showing one album's assets */
 static int g_album_open = -1;       /* index into g_album_* being shown */
@@ -301,6 +303,7 @@ static int grow_albums(int need)
 	    !GROW(g_album_nassets, c, need) ||
 	    !GROW(g_album_shared, c, need) ||
 	    !GROW(g_album_has_link, c, need) ||
+	    !GROW(g_album_updated, c, need) ||
 	    !(g_album_cap = GROW(g_album_cover, c, need)))
 		return 0;
 	return 1;