feat(tvldb): Import the tvldb/paroxysm source, add a Nix derivation

- This imports the tvldb (actually a thing called 'paroxysm') code
  from https://git.theta.eu.org/eta/paroxysm into the monorepo.
- Additionally, I did a nix thing, yay! \o/
  (well, with tazjin's help)
- 3p/default.nix needed modifying to whitelist pgsql.

Change-Id: Icdf13ca221650dde376f632bd2dd8a087af451bf
Reviewed-on: https://cl.tvl.fyi/c/depot/+/389
Reviewed-by: tazjin <mail@tazj.in>

fun/tvldb/src/schema.rs

@@ -0,0 +1,18 @@
+table! {
+    entries (id) {
+        id -> Int4,
+        keyword_id -> Int4,
+        idx -> Int4,
+        text -> Varchar,
+        creation_ts -> Timestamp,
+        created_by -> Varchar,
+    }
+}
+
+table! {
+    keywords (id) {
+        id -> Int4,
+        name -> Varchar,
+        chan -> Varchar,
+    }
+}