Move preview button to per-slot in edit form, remove card dropdown

- Preview button always visible next to Variables for each template slot
- Remove \n\n prefix from video_warning default value
- Use conditional {% if video_warning %} with blank line in templates
- Fix all .jinja2 files and inline defaults to match
- Add SVG favicon (camera + notification dot)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/routes/template-configs/+page.svelte

@@ -189,6 +189,8 @@
 							<div class="flex items-center justify-between mb-1">
 								<label class="text-xs text-[var(--color-muted-foreground)]">{t(`templateConfig.${slot.label}`)}</label>
 								<div class="flex items-center gap-2">
+									<button type="button" onclick={() => previewSlot(slot.key)}
+										class="text-xs text-[var(--color-muted-foreground)] hover:underline">{t('templateConfig.preview')}</button>
 									{#if varsRef[slot.key]}
 										<button type="button" onclick={() => showVarsFor = slot.key}
 											class="text-xs text-[var(--color-muted-foreground)] hover:underline">{t('templateConfig.variables')}</button>
@@ -204,13 +206,10 @@
 										<p class="mt-1 text-xs" style="color: var(--color-error-fg);">✕ {t('common.syntaxError')}: {slotErrors[slot.key]}{slotErrorLines[slot.key] ? ` (${t('common.line')} ${slotErrorLines[slot.key]})` : ''}</p>
 									{/if}
 								{/if}
-								{#if slotPreview[slot.key] && !slotErrors[slot.key]}
-									<details class="mt-1">
-										<summary class="text-xs text-[var(--color-muted-foreground)] cursor-pointer hover:underline">{t('templateConfig.preview')}</summary>
-										<div class="mt-1 p-2 bg-[var(--color-muted)] rounded text-sm">
-											<pre class="whitespace-pre-wrap">{slotPreview[slot.key]}</pre>
-										</div>
-									</details>
+								{#if slotPreview[slot.key]}
+									<div class="mt-1 p-2 bg-[var(--color-muted)] rounded text-sm">
+										<pre class="whitespace-pre-wrap">{slotPreview[slot.key]}</pre>
+									</div>
 								{/if}
 							{:else}
 								<input bind:value={(form as any)[slot.key]}