refactor(theme): remove 184 var() fallbacks — every one was unreachable

#2277 counted ~150 "raw colour literals bypassing the tokens". Measuring them
told a different story: 184 sat in `var(--token, #fallback)` position, and a
check against theme.css shows every one of those tokens IS declared. So the
fallbacks could not render. Not drift — vestigial.

They were also not this palette. The most common were Tailwind and Flat-UI
defaults — #6366f1 indigo, #22c55e green, #f59e0b amber, #3b82f6 blue,
#e74c3c and #27ae60 — a second, unsanctioned colour scheme sitting in the
codebase looking like the app's colours to anyone reading it.

Removing them is not tidying. #2319's lesson is that a fallback is WORSE than a
missing token: a missing token renders as nothing and someone eventually
notices, while a fallback renders something plausible forever. These 184 were
one token rename away from silently repainting the app in Tailwind. The design
token check would catch the rename — but the fallback is precisely the thing
that would make it invisible if the check were ever bypassed.

Literal count 152 -> 45, which matters beyond the number: a report that is
mostly unreachable noise is one people stop reading, and then it stops working
while still passing. What remains should be genuinely worth looking at.

Done with a paren-aware transform, not a regex — `var(--x, rgba(0,0,0,.5))`
nests parens and `[^)]+` would cut at the first one and leave `))` behind.
Verified after: every changed line is a fallback strip and nothing else, and
every var() reference still resolves.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UaYUaouG9jjhATyuxCKrQs

frontend/src/views/TrashView.vue

@@ -68,7 +68,7 @@ onMounted(() => store.fetchTrash());
 .batch-count { opacity: 0.6; font-weight: 400; font-size: 0.9em; margin-left: 0.35rem; }
 .batch-meta { font-size: 0.82em; opacity: 0.6; margin-top: 0.25rem; }
 .batch-actions { display: flex; gap: 0.5rem; flex-shrink: 0; }
-.batch-actions button { border-radius: 6px; padding: 0.35rem 0.7rem; cursor: pointer; border: 1px solid var(--color-border, #2a2a2e); background: none; color: inherit; }
+.batch-actions button { border-radius: 6px; padding: 0.35rem 0.7rem; cursor: pointer; border: 1px solid var(--color-border); background: none; color: inherit; }
 .btn-restore:hover { border-color: var(--color-action-primary); color: var(--color-action-primary); }
 .btn-purge:hover { border-color: var(--color-action-destructive); color: var(--color-action-destructive); }
 </style>