chore: upgrade templ v0.3.1001 → v0.3.1020, pin in Dockerfile

Newer templ generates ResolveAttributeValue calls that don't exist in
v0.3.1001 runtime, causing Docker build failures ("undefined:
templ.ResolveAttributeValue"). Pin templ CLI version in Dockerfile to
match go.mod instead of using @latest.

Also updated local templ CLI to v0.3.1020 to match.

Dockerfile

@@ -11,7 +11,7 @@ RUN wget -O /tmp/sqlc.tar.gz https://github.com/sqlc-dev/sqlc/releases/download/
     tar -xzf /tmp/sqlc.tar.gz -C /usr/local/bin sqlc && \
     rm /tmp/sqlc.tar.gz
 RUN --mount=type=cache,target=/root/go/pkg/mod \
-  go install github.com/a-h/templ/cmd/templ@latest
+  go install github.com/a-h/templ/cmd/templ@v0.3.1020
 
 # Copy package files and install npm dependencies (cached unless package.json changes)
 COPY package*.json ./