feat: locale-aware command templates, debounced auto-sync, entity pickers

- Locale-aware templates: CommandTemplateSlot now has a locale column,
  allowing each slot to have per-language variants (EN/RU). Templates
  are resolved at runtime from the Telegram user's language_code.

- Merged system configs: "Default Commands (EN)" and "(RU)" merged
  into a single "Default Commands" config with locale-aware slots.
  Migration handles existing data automatically.

- Configurable command descriptions: hardcoded COMMAND_DESCRIPTIONS
  replaced with desc_* template slots (desc_status, desc_help, etc.)
  that users can customize per locale. setMyCommands registers all
  locales explicitly.

- Removed locale from CommandConfig: no longer needed since locale
  is derived from the Telegram user's language at runtime.

- Debounced command auto-sync: after command config/tracker changes,
  affected bots are marked dirty and synced after a 30s debounce
  window. Manual "Sync with Telegram" button still works.

- Entity pickers in LinkedTargetsSection: replaced 6 plain <select>
  elements with EntitySelect components (search, icons, keyboard nav).
  Added onselect callback and size="sm" props to EntitySelect.

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

@@ -310,7 +310,6 @@ class CommandConfig(SQLModel, table=True):
     name: str
     icon: str = Field(default="")
     enabled_commands: list[str] = Field(default_factory=list, sa_column=Column(JSON))
-    locale: str = Field(default="en")
     response_mode: str = Field(default="media")  # "media" or "text"
     default_count: int = Field(default=5)
     rate_limits: dict[str, Any] = Field(default_factory=dict, sa_column=Column(JSON))
@@ -336,19 +335,22 @@ class CommandTemplateConfig(SQLModel, table=True):
 
 
 class CommandTemplateSlot(SQLModel, table=True):
-    """One Jinja2 template for a specific command response slot.
+    """One Jinja2 template for a specific command response slot and locale.
 
     Slot names match command names (e.g. 'status', 'help', 'albums').
+    Description slots use 'desc_' prefix (e.g. 'desc_status', 'desc_help').
+    Each (config, slot, locale) triple holds a separate template.
     """
 
     __tablename__ = "command_template_slot"
     __table_args__ = (
-        UniqueConstraint("config_id", "slot_name", name="uq_command_template_slot"),
+        UniqueConstraint("config_id", "slot_name", "locale", name="uq_cmd_slot_locale"),
     )
 
     id: int | None = Field(default=None, primary_key=True)
     config_id: int = Field(foreign_key="command_template_config.id", index=True)
     slot_name: str
+    locale: str = Field(default="en")
     template: str = Field(default="", sa_column=Column(Text, default=""))