fix: Windows path handling, light theme default, file viewer in editor, first-user admin logic

Config:
- Fixed SQLite path parsing on Windows (handle drive letters without prepending /)
- Changed default theme from dark to light
- Updated OAuth test credentials (gitea_oauth_client_id/secret)

Auth:
- First real user (excluding default admin with no password) becomes admin
- Changed user count query to exclude users without password_hash

File viewer:
- Removed separate _render_file_viewer() —

app/routers/board.py

@@ -926,10 +926,6 @@ async def view_page(request: Request, page_id: int):
             return HTMLResponse("<h2>Page not found</h2>", status_code=404)
     page = dict(row)
 
-    # ── File viewer for uploaded files ──
-    if page.get("content_format") == "file":
-        return _render_file_viewer(page, request)
-
     ws = page.get("workspace", "")
     parts = ws.split("/") if "/" in ws else ["", ""]
     owner, repo = parts[0], parts[1] if len(parts) > 1 else ""
@@ -941,10 +937,38 @@ async def view_page(request: Request, page_id: int):
         fav = conn.execute(
             "SELECT id FROM favorites WHERE user_id=? AND page_id=?", (uid, page_id)
         ).fetchone()
+
+    # Build page_data, including file metadata for uploaded files
+    page_data = {"id": page_id, "title": page.get("title"), "content_format": page.get("content_format", "blocks"), "content": page.get("content", ""), "favorited": fav is not None, "share_mode": page.get("share_mode", "private"), "published": bool(page.get("published", 0))}
+
+    # For file pages, extract file metadata and add to page_data
+    if page.get("content_format") == "file":
+        import json as _json
+        try:
+            meta = _json.loads(page.get("content", "{}"))
+        except _json.JSONDecodeError:
+            meta = {}
+        file_path = meta.get("file_path", "").replace("\\", "/")
+        mime_type = meta.get("mime_type", "application/octet-stream")
+        file_size = meta.get("size", 0)
+        # Build workspace_id from file_path
+        fp_parts = file_path.split("/")
+        ws_id = ""
+        for p in fp_parts:
+            if p.startswith("workspace_"):
+                ws_id = p.replace("workspace_", "")
+                break
+        filename = fp_parts[-1] if fp_parts else page.get("title", "File")
+        file_url = f"/api/files/{ws_id}/{filename}" if ws_id else ""
+        page_data["file_url"] = file_url
+        page_data["file_mime"] = mime_type
+        page_data["file_size"] = file_size
+        page_data["file_name"] = filename
+
     ctx = {**sidebar, "page": page, "page_favorited": fav is not None,
            "page_share_mode": page.get("share_mode", "private"),
            "page_published": bool(page.get("published", 0)),
-           "page_data": {"id": page_id, "title": page.get("title"), "content_format": page.get("content_format", "blocks"), "content": page.get("content", ""), "favorited": fav is not None, "share_mode": page.get("share_mode", "private"), "published": bool(page.get("published", 0))}}
+           "page_data": page_data}
     template = env.get_template("page_editor.html")
     response = template.render(**ctx)
     return HTMLResponse(content=response, headers={"Cache-Control": "no-store, max-age=0"})