feat(web): add @memoh/icon package and unify brand icon system

Replace FontAwesome/CDN brand icons with local SVG-based Vue components
in a new shared @memoh/icon package. Provider icon URLs in conf/providers
YAML files are replaced with preset names, intercepted by ProviderIcon
component on the frontend. SearchProviderLogo and ChannelIcon components
are migrated to @memoh/icon. All icon containers now use a unified
circular gray (rounded-full bg-muted) style. Adds wechat and matrix
channel icons.

mise.toml

@@ -52,6 +52,10 @@ depends = [
 description = "Generate SQL code"
 run = "sqlc generate"
 
+[tasks.icons-generate]
+description = "Generate icon Vue components from SVG sources"
+run = "pnpm --filter @memoh/icon generate"
+
 [tasks.dev]
 description = "Start development environment"
 run = """