Cleaner left rail and a pinned frame toolbar

[ankitsejwal]

Tidies up the editor chrome after the three-column move.

• The left rail now leads with a black Add photos button (same look as Export PDF) instead of the dashed dropzone. The drop box is hidden until you actually start dragging — then a square pad fades in over a blurred strip, so the default state stays clean but drag-and-drop still works.
• Shortened the subhead to "Edit each frame on the page — everything stays on your device."
• Dropped the "Print sheet (A4)" line above the page — the sheet speaks for itself.
• Per-row is a +/- stepper now rather than a slider; easier to land on an exact number.
• The frame toolbar floats as a pill pinned to the bottom of the screen (Figma-style) so selecting a frame no longer nudges the whole page down. Trimmed it to an icon-only trash and a tick instead of the "Remove"/"Done" text.