feat(plugins): add TimeNow function to SchedulerService (#4337)

* feat: add TimeNow function to SchedulerService plugin

Added new TimeNow RPC method to the SchedulerService host service that returns
the current time in two formats: RFC3339Nano string and Unix milliseconds int64.
This provides plugins with a standardized way to get current time information
from the host system.

The implementation includes:
- TimeNowRequest/TimeNowResponse protobuf message definitions
- Go host service implementation using time.Now()
- Complete test coverage with format validation
- Generated WASM interface code for plugin communication

* feat: add LocalTimeZone field to TimeNow response

Added LocalTimeZone field to TimeNowResponse message in the SchedulerService
plugin host service. This field contains the server's local timezone name
(e.g., 'America/New_York', 'UTC') providing plugins with timezone context
alongside the existing RFC3339Nano and Unix milliseconds timestamps.

The implementation includes:
- New local_time_zone protobuf field definition
- Go implementation using time.Now().Location().String()
- Updated test coverage with timezone validation
- Generated protobuf serialization/deserialization code

* docs: update plugin README with TimeNow function documentation

Updated the plugins README.md to document the new TimeNow function in the
SchedulerService. The documentation includes detailed descriptions of the
three return formats (RFC3339Nano, UnixMilli, LocalTimeZone), practical
use cases, and a comprehensive Go code example showing how plugins can
access current time information for logging, calculations, and timezone-aware
operations.

* docs: remove wrong comment from InitRequest

Signed-off-by: Deluan <deluan@navidrome.org>

* fix: add missing TimeNow method to namedSchedulerService

Added TimeNow method implementation to namedSchedulerService struct to satisfy the scheduler.SchedulerService interface contract. This method was recently added to the interface but the namedSchedulerService wrapper was not updated, causing compilation failures in plugin tests. The implementation is a simple pass-through to the underlying scheduler service since TimeNow doesn't require any special handling for named callbacks.

---------

Signed-off-by: Deluan <deluan@navidrome.org>

plugins/README.md

@@ -196,7 +196,7 @@ See the [cache.proto](host/cache/cache.proto) file for the full API definition.
 
 #### SchedulerService
 
-The SchedulerService provides a unified interface for scheduling both one-time and recurring tasks. See the [scheduler.proto](host/scheduler/scheduler.proto) file for the full API.
+The SchedulerService provides a unified interface for scheduling both one-time and recurring tasks, as well as accessing current time information. See the [scheduler.proto](host/scheduler/scheduler.proto) file for the full API.
 
 ```protobuf
 service SchedulerService {
@@ -208,11 +208,50 @@ service SchedulerService {
 
    // Cancel any scheduled job
    rpc CancelSchedule(CancelRequest) returns (CancelResponse);
+
+   // Get current time in multiple formats
+   rpc TimeNow(TimeNowRequest) returns (TimeNowResponse);
 }
 ```
 
+**Key Features:**
+
 - **One-time scheduling**: Schedule a callback to be executed once after a specified delay.
 - **Recurring scheduling**: Schedule a callback to be executed repeatedly according to a cron expression.
+- **Current time access**: Get the current time in standardized formats for time-based operations.
+
+**TimeNow Function:**
+
+The `TimeNow` function returns the current time in three formats:
+
+```protobuf
+message TimeNowResponse {
+    string rfc3339_nano = 1;     // RFC3339 format with nanosecond precision
+    int64 unix_milli = 2;        // Unix timestamp in milliseconds
+    string local_time_zone = 3;  // Local timezone name (e.g., "UTC", "America/New_York")
+}
+```
+
+This allows plugins to:
+
+- Get high-precision timestamps for logging and event correlation
+- Perform time-based calculations using Unix timestamps
+- Handle timezone-aware operations by knowing the server's local timezone
+
+Example usage:
+
+```go
+// Get current time information
+timeResp, err := scheduler.TimeNow(ctx, &scheduler.TimeNowRequest{})
+if err != nil {
+    return err
+}
+
+// Use the different time formats
+timestamp := timeResp.Rfc3339Nano     // "2024-01-15T10:30:45.123456789Z"
+unixMs := timeResp.UnixMilli          // 1705312245123
+timezone := timeResp.LocalTimeZone    // "UTC"
+```
 
 Plugins using this service must implement the `SchedulerCallback` interface:
 
@@ -433,7 +472,7 @@ If no permissions are needed, use an empty permissions object: `"permissions": {
 The following permission keys correspond to host services:
 
 | Permission    | Host Service       | Description                                        | Required Fields                                       |
-|---------------|--------------------|----------------------------------------------------|-------------------------------------------------------|
+| ------------- | ------------------ | -------------------------------------------------- | ----------------------------------------------------- |
 | `http`        | HttpService        | Make HTTP requests (GET, POST, PUT, DELETE, etc..) | `reason`, `allowedUrls`                               |
 | `websocket`   | WebSocketService   | Connect to and communicate via WebSockets          | `reason`, `allowedUrls`                               |
 | `cache`       | CacheService       | Store and retrieve cached data with TTL            | `reason`                                              |