* fix(server): render image paths with spaces
Raw spaces in local Markdown image destinations made the renderer treat provider images as text. Emit encoded file URIs for spaced paths so the client parses and resolves them as images.
* fix(server): encode all absolute image paths
Provider image paths without spaces could still contain URI-significant characters such as fragment or query markers. Route every absolute local path through the encoded file URI boundary.
* fix(server): encode network image paths
Windows network-share paths bypassed the absolute local path handling. Normalize UNC and extended UNC paths before encoding them as file URIs.
* fix(app): preserve network image paths
Host-based file URIs were decoded as relative paths. Restore the UNC prefix so provider images on network shares resolve through the file RPC correctly.
* fix(server): preserve double-slash POSIX image paths
Classify only backslash-prefixed paths as Windows network paths so POSIX double-leading-slash paths retain their filesystem semantics.
