Replace scs postgresstore with a sqlc-backed SessionStore.

Keep scs for cookies and session API while sessions DDL and queries live in the same sqlc stack as the rest of Postgres.

go.sum

@@ -1,5 +1,3 @@
-github.com/alexedwards/scs/postgresstore v0.0.0-20251002162104-209de6e426de h1:LDrMkjj4OCCQsq9SvIPQV1l3leMxqXZTCTxDFwMrqTE=
-github.com/alexedwards/scs/postgresstore v0.0.0-20251002162104-209de6e426de/go.mod h1:TDDdV/xnjj+/4zBQ9a2k+i2AbuAdY7SQjPUh5zoTZ3M=
 github.com/alexedwards/scs/v2 v2.9.0 h1:xa05mVpwTBm1iLeTMNFfAWpKUm4fXAW7CeAViqBVS90=
 github.com/alexedwards/scs/v2 v2.9.0/go.mod h1:ToaROZxyKukJKT/xLcVQAChi5k6+Pn1Gvmdl7h3RRj8=
 github.com/aws/aws-sdk-go-v2 v1.43.7 h1:msCzvkeYJA9ehbV8mRRmkZLo/zJg/+yDVLNtflg83hQ=
@@ -43,8 +41,6 @@ github.com/jackc/puddle/v2 v2.2.2 h1:PR8nw+E/1w0GLuRFSmiioY6UooMp6KJv0/61nB7icHo
 github.com/jackc/puddle/v2 v2.2.2/go.mod h1:vriiEXHvEE654aYKXXjOvZM39qJ0q+azkZFrfEOc3H4=
 github.com/joho/godotenv v1.5.1 h1:7eLL/+HRGLY0ldzfGMeQkb7vMd0as4CfYvUVzLqw0N0=
 github.com/joho/godotenv v1.5.1/go.mod h1:f4LDr5Voq0i2e/R5DDNOoa2zzDfwtkZa6DnEwAbqwq4=
-github.com/lib/pq v1.4.0 h1:TmtCFbH+Aw0AixwyttznSMQDgbR5Yed/Gg6S8Funrhc=
-github.com/lib/pq v1.4.0/go.mod h1:5WUZQaWbwv1U+lTReE5YruASi9Al49XbQIvNi/34Woo=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=