feat(tg-fitness-bot): initial Telegram workout tracker bot

Python bot that parses workout messages (Exercise: SetsxRepsxWeight),
detects supersets from consecutive lines, extracts machine IDs, stores
both raw message text and parsed data in SQLite, and reads original
timestamps from forwarded Saved Messages.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

flake.nix

@@ -0,0 +1,40 @@
+{
+  description = "BigBiggerBiggestBot — Telegram fitness tracker";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, flake-utils }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = nixpkgs.legacyPackages.${system};
+
+        python = pkgs.python3;
+
+        pythonEnv = python.withPackages (ps: with ps; [
+          python-telegram-bot
+          python-dotenv
+        ]);
+      in
+      {
+        # `nix develop` — drop into a shell with everything available
+        devShells.default = pkgs.mkShell {
+          packages = [ pythonEnv ];
+          shellHook = ''
+            echo "💪 BigBiggerBiggestBot dev shell"
+            echo "   Run:  python bot.py"
+          '';
+        };
+
+        # `nix run` — start the bot from the current directory
+        apps.default = {
+          type = "app";
+          program = toString (pkgs.writeShellScript "run-bot" ''
+            exec ${pythonEnv}/bin/python "$PWD/bot.py"
+          '');
+        };
+      }
+    );
+}