Add multi-route donor->recipient support, fix VK hashtag truncation

Posts can now be sourced from multiple VK groups, each routed to its own
Telegram/MAX destination(s) with independent on/off switches, configured
via data/routes.json (supports // line comments). Falls back to a single
route auto-generated from the legacy VK_SOURCE/TG_CHAT_ID/MAX_CHAT_ID env
vars if routes.json doesn't exist yet, so existing deployments keep working.

Routes are processed strictly sequentially within a cycle (no concurrency)
to keep flood control on VK/TG/MAX correct, since bot tokens are shared
across routes. DB schema gains route_id in the posts uniqueness key so the
same VK donor can safely feed multiple routes without status collisions.

Also removes the trailing-hashtag-stripping logic in text_formatter, which
was silently deleting VK posts' own hashtags whenever COMMON_TAGS wasn't
configured (it always wasn't) - posts are now forwarded unchanged.

routes.json.example

@@ -0,0 +1,25 @@
+[
+
+// redairsoft_main
+{
+  "id": "redairsoft_main",
+  "name": "Red Airsoft (основная группа)",
+  "vk_source": "public36860851",
+  "tg_chat_id": "-1001303630155",
+  "tg_enabled": true,
+  "max_chat_id": "123456",
+  "max_enabled": true
+},
+
+// second_donor - только в TG, MAX выключен
+{
+  "id": "second_donor",
+  "name": "Вторая донор-группа",
+  "vk_source": "someothergroup",
+  "tg_chat_id": "-1009999999999",
+  "tg_enabled": true,
+  "max_chat_id": "",
+  "max_enabled": false
+}
+
+]