feat: locale-aware notification templates + UX improvements

- Add locale support to notification templates (matching command template
  pattern): TemplateSlot now has locale field with (config_id, slot_name,
  locale) uniqueness, nested API format {slot: {locale: template}}
- Migration merges separate EN/RU system configs into unified per-provider
  configs; seeds create one config per provider with multi-locale slots
- Locale-aware dispatch with EN fallback in NotificationDispatcher
- Frontend locale tabs (EN/RU) on template config editor
- Fix tracking config cards not showing default provider icons
- Global provider filter, search palette, and various UX polish

packages/server/src/notify_bridge_server/database/seeds.py

@@ -30,7 +30,11 @@ async def _seed_provider_template(
     provider_type: str,
     label: str,
 ) -> None:
-    """Seed templates for a single provider type across all locales."""
+    """Seed templates for a single provider type across all locales.
+
+    Creates a single TemplateConfig per provider with locale-aware slots
+    (each slot has an EN and RU version stored as separate rows).
+    """
     from notify_bridge_core.templates.defaults import load_default_templates
 
     result = await session.exec(
@@ -40,80 +44,42 @@ async def _seed_provider_template(
         )
     )
     configs = result.all()
-    existing_locales = {
-        (c.locale if c.locale else ("ru" if "(RU)" in c.name else "en")): c
-        for c in configs
-    }
+
+    if not configs:
+        config = TemplateConfig(
+            user_id=0,
+            provider_type=provider_type,
+            name=f"Default {label}",
+            description=f"Default {label} templates",
+        )
+        session.add(config)
+        await session.flush()
+    else:
+        config = configs[0]
 
     for locale in ("en", "ru"):
         slots = load_default_templates(locale, provider_type=provider_type)
         if not slots:
             continue
-
-        if locale not in existing_locales:
-            now = datetime.now(timezone.utc).isoformat()
-            name = f"Default {label} ({locale.upper()})"
-            desc = f"Default {label} templates ({locale.upper()})"
-            # Get column names to build INSERT with defaults for legacy cols
-            col_info = (await session.execute(
-                text("PRAGMA table_info(template_config)")
-            )).fetchall()
-            col_names = [c[1] for c in col_info if c[1] != "id"]
-            values: dict[str, object] = {}
-            for col in col_names:
-                if col == "user_id":
-                    values[col] = 0
-                elif col == "provider_type":
-                    values[col] = provider_type
-                elif col == "name":
-                    values[col] = name
-                elif col == "description":
-                    values[col] = desc
-                elif col == "created_at":
-                    values[col] = now
-                elif col == "date_format":
-                    values[col] = "%d.%m.%Y, %H:%M UTC"
-                elif col == "date_only_format":
-                    values[col] = "%d.%m.%Y"
-                elif col == "locale":
-                    values[col] = locale
-                else:
-                    values[col] = ""  # empty string for legacy columns
-            cols_str = ", ".join(values.keys())
-            placeholders = ", ".join(f":{k}" for k in values.keys())
-            await session.execute(
-                text(f"INSERT INTO template_config ({cols_str}) VALUES ({placeholders})"),
-                values,
+        for slot_name, template_text in slots.items():
+            slot_result = await session.exec(
+                select(TemplateSlot).where(
+                    TemplateSlot.config_id == config.id,
+                    TemplateSlot.slot_name == slot_name,
+                    TemplateSlot.locale == locale,
+                )
             )
-            config_id = (await session.execute(
-                text("SELECT last_insert_rowid()")
-            )).scalar()
-
-            for slot_name, template_text in slots.items():
+            existing = slot_result.first()
+            if existing:
+                existing.template = template_text
+                session.add(existing)
+            else:
                 session.add(TemplateSlot(
-                    config_id=config_id,
+                    config_id=config.id,
                     slot_name=slot_name,
+                    locale=locale,
                     template=template_text,
                 ))
-        else:
-            config = existing_locales[locale]
-            for slot_name, template_text in slots.items():
-                slot_result = await session.exec(
-                    select(TemplateSlot).where(
-                        TemplateSlot.config_id == config.id,
-                        TemplateSlot.slot_name == slot_name,
-                    )
-                )
-                existing = slot_result.first()
-                if existing:
-                    existing.template = template_text
-                    session.add(existing)
-                else:
-                    session.add(TemplateSlot(
-                        config_id=config.id,
-                        slot_name=slot_name,
-                        template=template_text,
-                    ))
 
 
 async def _seed_provider_command_template(