Viewer: save to Vita, turn with L/R; album name order, cover shape setting

- Inside an album, SELECT cycles newest / oldest / file name A-Z / Z-A
  (natural, case-insensitive; name orders drop the month headers and
  L/R jump by initial letter). Asset originalFileName is now parsed.
- Full-screen viewer: Triangle or the "Save to Vita" button downloads
  the original (falling back to Immich's full-size / preview JPEG) and
  exports it to the Photos app via ScePhotoExport (new src/export.c).
  The video downloader is now a generic download_to_file().
- R / L turn the whole viewer 90 degrees clockwise / counter-clockwise
  so the Vita can be held upright (new src/viewrot.c): it renders into
  a portrait render target drawn rotated, and maps d-pad, sticks and
  touch into the turned screen. Zoom moves to the right stick only.
  SCREEN_W/H are now variables for that logical screen.
- Server & Backup page: album cover shape setting (vertical 3:4,
  square, panoramic 16:9), saved as covershape= in config.txt.
- Test builds: "rup" holds the right stick up in test_input.txt.

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

src/main.c

@@ -42,6 +42,7 @@
 #include <psp2/net/netctl.h>
 #include <psp2/sysmodule.h>
 #include <psp2/ime_dialog.h>
+#include <psp2/photoexport.h>
 #include <psp2/common_dialog.h>
 
 #include <vita2d.h>
@@ -54,8 +55,11 @@
 #define JSMN_PARENT_LINKS
 #include "jsmn.h"
 
-#define SCREEN_W 960
-#define SCREEN_H 544
+/* the logical screen the UI lays itself out in: 960x544, except while the
+ * rotated photo viewer draws into its portrait render target (544x960) */
+static int g_screen_w = 960, g_screen_h = 544;
+#define SCREEN_W g_screen_w
+#define SCREEN_H g_screen_h
 
 #define COLS       5     /* rough items per row, for prefetch distances only */
 #define ROW_H      200   /* justified-grid row height; widths follow aspect */
@@ -124,6 +128,7 @@ static vita2d_texture *g_ic_both;
  * buffers), so a realloc here can't dangle a pointer under it. */
 static char (*g_asset_ids)[40];
 static char (*g_asset_dates)[DATELEN]; /* YYYY-MM-DDTHH:MM:SS */
+static char (*g_asset_names)[64];      /* originalFileName, "" = unknown */
 static float *g_asset_ratio;           /* display w/h from exif, 0 = unknown */
 static unsigned char *g_asset_rot;     /* raw exif orientation (0 = none) */
 static unsigned char *g_asset_is_video;
@@ -162,5 +167,7 @@ static char (*g_tex_err)[160];
 #include "map.c"       /* geotag map: markers, clustering, projection    */
 #include "albums.c"    /* album list page + album open/fetch threads     */
 #include "video.c"     /* video download + SceAvPlayer playback          */
+#include "export.c"    /* save a photo to the Vita's Photos app          */
+#include "viewrot.c"   /* L/R-turned photo viewer (render target)        */
 #include "sync.c"      /* local scan/hash/check/upload + sync overview   */
 #include "app.c"       /* main(): init, event loop, threads             */