Item sprites — swap procedural draw for tileset icons

Stone, iron ore, gold, wood, plank now render as ElvGames FG_Abandoned_Mines
sprites instead of hue-hashed coloured squares. Other types fall back to the
procedural square; quality border + stack count badge are layered on top of
whichever base renders.

Atlas coords picked from /tmp/item_finals.png + /tmp/wood_plank_alts.png:
  stone     (5, 33)   rock cluster with stone chunks
  iron_ore  (9, 33)   rock with silver chunks
  gold      (13, 33)  rock with gold chunks
  wood      (20, 13)  chunky brown log pile
  plank     (28, 18)  horizontal-grain plank stack

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

art/tiles/FG_Abandoned_Mines.png.import

@@ -0,0 +1,40 @@
+[remap]
+
+importer="texture"
+type="CompressedTexture2D"
+uid="uid://ba6umi3eb8p65"
+path="res://.godot/imported/FG_Abandoned_Mines.png-59627b415a268a4512cae2e47f098866.ctex"
+metadata={
+"vram_texture": false
+}
+
+[deps]
+
+source_file="res://art/tiles/FG_Abandoned_Mines.png"
+dest_files=["res://.godot/imported/FG_Abandoned_Mines.png-59627b415a268a4512cae2e47f098866.ctex"]
+
+[params]
+
+compress/mode=0
+compress/high_quality=false
+compress/lossy_quality=0.7
+compress/uastc_level=0
+compress/rdo_quality_loss=0.0
+compress/hdr_compression=1
+compress/normal_map=0
+compress/channel_pack=0
+mipmaps/generate=false
+mipmaps/limit=-1
+roughness/mode=0
+roughness/src_normal=""
+process/channel_remap/red=0
+process/channel_remap/green=1
+process/channel_remap/blue=2
+process/channel_remap/alpha=3
+process/fix_alpha_border=true
+process/premult_alpha=false
+process/normal_map_invert_y=false
+process/hdr_as_srgb=false
+process/hdr_clamp_exposure=false
+process/size_limit=0
+detect_3d/compress_to=1