Fix dialyzer warnings and improve type safety

- Fix Packet module usage in queries (use from/1 to create proper query)
- Fix error handling in DbOptimizer to use try/rescue
- Remove unused erlc_paths from mix.exs comment
- Improve type specifications consistency

All dialyzer specs now pass without critical errors.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

lib/aprsme/db_optimizer.ex

@@ -66,8 +66,10 @@ defmodule Aprsme.DbOptimizer do
           opts
         )
 
-      case Repo.insert_all(schema, batch, insert_opts) do
-        {count, _} -> {:ok, count}
+      try do
+        {count, _} = Repo.insert_all(schema, batch, insert_opts)
+        {:ok, count}
+      rescue
         error -> {:error, error}
       end
     end)

lib/aprsme/packets.ex

@@ -382,7 +382,7 @@ defmodule Aprsme.Packets do
     bounds = Map.get(opts, :bounds)
 
     query =
-      Packet
+      from(p in Packet)
       |> QueryBuilder.with_position()
       |> QueryBuilder.with_time_range(opts)
       |> QueryBuilder.maybe_filter_region(opts)
@@ -416,7 +416,7 @@ defmodule Aprsme.Packets do
     bounds = Map.get(opts, :bounds)
 
     query =
-      Packet
+      from(p in Packet)
       |> QueryBuilder.with_position()
       |> QueryBuilder.with_time_range(opts)
       |> QueryBuilder.maybe_filter_region(opts)