fix: fail loud on missing emoji dir, stem collisions, and corrupt images

refresh() previously treated a missing assets/emojis folder (wrong cwd,
missing WorkingDirectory=/WORKDIR) as an empty one, silently deleting
every application emoji on the app every restart with no signal and no
way back (recreated emojis get new IDs). _scan_folder now raises
DPYAppEmojisError naming the absent path instead; a present-but-empty
folder still mirrors as before.

Two files sharing a name stem across extensions (check.png + check.gif)
used to silently collapse to one synced emoji via last-write-wins,
breaking the documented delete+re-add replace workflow with no error.
_scan_folder now raises DPYAppEmojisError naming both colliding files.

A valid extension with unrecognized magic bytes (truncated download,
mismatched format) made discord.py raise an anonymous
ValueError('Unsupported image type given') from create_application_emoji,
which the lib's (Forbidden, HTTPException) catch didn't cover, leaving
no way to tell which file in a large folder was broken. _scan_folder now
pre-flights the same magic-byte check discord.py itself uses and raises
ValueError naming the offending file before any create is attempted.

Also collapses the redundant Forbidden member in the create/delete except
clauses (Forbidden already subclasses HTTPException); log-then-raise
behavior is unchanged.

Bump 0.1.0 -> 0.1.1.

Signed-off-by: disqualifier <dev@disqualifier.me>

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "dpy_appemojis"
-version = "0.1.0"
+version = "0.1.1"
 description = "Mirror a project folder onto the bot's application emojis for discord.py — folder is the source of truth. Config-free, injectable, installable."
 requires-python = ">=3.10"
 dependencies = [