fix(encoding): strip all non-ASCII chars from all Python source files

GitHub Actions runner was failing with:
UnicodeDecodeError: utf-8 codec cannot decode byte 0x97

Root cause: em dashes (U+2014 --), arrows (U+2192 ->), and other
Unicode punctuation in comments across all 8 files we added/modified.
The runner's system locale read api/main.py as bytes and hit the
multi-byte UTF-8 sequence for -- at byte position 436.

Fix: replaced all non-ASCII chars with ASCII equivalents in all files:
U+2014 (em dash) -> --
U+2192 (arrow) -> ->
all curly quotes -> straight quotes

Also moved route-check logic to scripts/verify_routes.py which uses
explicit encoding='utf-8' to be runner-locale independent.

scripts/verify_routes.py

@@ -1,4 +1,5 @@
 #!/usr/bin/env python3
+"""CI check: verify all route modules in api/main.py exist on disk."""
 import re, os, sys
 
 def verify_routes():
@@ -10,15 +11,16 @@ def verify_routes():
         sys.exit(1)
 
     m = re.findall(r'from api\.routes import (.*)', main)
-    if m:
-        mods = [x.strip() for x in m[0].split(',')]
-        missing = [x for x in mods if not os.path.exists(f'api/routes/{x}.py')]
-        if missing:
-            print('MISSING ROUTE FILES:', missing)
-            sys.exit(1)
-        print(f'PASS: All {len(mods)} route files present')
-    else:
-        print('PASS: No route imports to check')
+    if not m:
+        print("PASS: no route imports found")
+        return
+
+    mods = [x.strip() for x in m[0].split(',')]
+    missing = [x for x in mods if not os.path.exists(f'api/routes/{x}.py')]
+    if missing:
+        print('MISSING ROUTE FILES:', missing)
+        sys.exit(1)
+    print(f'PASS: All {len(mods)} route files present')
 
 if __name__ == '__main__':
     verify_routes()