fix: cache button renders on single page; cache_button edit swallows deleted/expired message (v0.1.7)

update_buttons gated the cache button behind the nav row, so a single-page
paginator with a non-empty cache never showed it despite the README promising
otherwise; the cache button now renders whenever self.cache is truthy,
independent of nav, and start() keeps the view alive for that case too.

cache_button's post-sleep message.edit was unguarded, so a message deleted or
expired during cache_sleep raised out of the callback; it now mirrors
on_timeout's NotFound/Forbidden swallow and HTTPException log.

also compresses the module and method docstrings (no behavior change).

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

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "dpy_paginator"
-version = "0.1.6"
+version = "0.1.7"
 description = "Button-navigated paginator for discord.py — config-free, injectable emojis, installable."
 requires-python = ">=3.10"
 dependencies = [