Drop PaperMod theme, use minimal self-contained templates

PaperMod's opengraph.html calls partial with a redundant "partials/"
prefix that the production Hugo version (0.154.5, from the
hugomods/hugo:exts build image) doesn't tolerate, breaking the build.
Rather than patch a vendored theme, replaced it with plain, dependency-
free layouts (baseof/index/single/list) that render the actual homepage
content directly. Verified building successfully against the exact
Hugo image/version the deploy pipeline uses.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

hugo.toml

@@ -1,32 +1,17 @@
 baseURL = "https://www.reground.org/"
 locale = "en-US"
 title = "ReGround"
-theme = "PaperMod"
 
 enableRobotsTXT = true
 buildDrafts = false
 buildFuture = false
 buildExpired = false
+disableKinds = ["taxonomy", "term"]
 
 [params]
   env = "production"
   description = "ReGround helps fiction authors find the readers who were always meant to find them."
   author = "Will Estes"
-  defaultTheme = "auto"
-  disableThemeToggle = false
-  ShowReadingTime = false
-  ShowShareButtons = false
-  ShowPostNavLinks = false
-  ShowBreadCrumbs = false
-  ShowCodeCopyButtons = false
-  ShowRssButtonInSectionTermList = false
-  ShowToc = false
-  disableSpecial1stPost = true
-  hidemeta = true
-  mainSections = ["posts"]
-
-  [params.label]
-    text = "ReGround"
 
 # Menu is intentionally minimal for now — add Blog/About/Contact
 # entries here as those sections come online.