…tion logic (dotnet#5197)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: premun <7013027+premun@users.noreply.github.com>
Co-authored-by: Premek Vysoky <premek.vysoky@microsoft.com>

…development (dotnet#5203)

## New Filter Types
Added 4 new filter keywords to help distinguish between different types of VMR codeflow subscriptions:
- `:ff` and `:forwardflow` - filters for forward flows (source-enabled subscriptions with target directory)
- `:bf` and `:backflow` - filters for backflows (source-enabled subscriptions with source directory)

These filters use the existing `IsForwardFlow()` and `IsBackflow()` extension methods on the `Subscription` class.

## Partial Matching Auto-completion
Enhanced the filter system to automatically expand partial filter matches when unambiguous:
- Typing `:c` automatically applies `:codeflow`
- Typing `:forward` expands to `:forwardflow`
- Typing `:back` expands to `:backflow`
- Ambiguous cases like `:f` (could match `:ff` or `:forwardflow`) don't expand

…ipProperty` dependencies (dotnet#5209)

dotnet#5150
Also removes `<?xml version="1.0" encoding="utf-8"?>` from
VersionDetails.props, because it was not needed, since it's an msbuild
file

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

This PR implements validation to prevent misconfigured VMR codeflow
subscriptions that could lead to conflicts and operational issues, while
also improving the API design by unifying subscription querying methods.

## Problem

Currently, it's possible to create conflicting codeflow subscriptions
that can cause problems:

1. **Backflow conflicts**: Multiple VMR→repository subscriptions
targeting the same repository branch
2. **Forward flow conflicts**: Multiple repository→VMR subscriptions
flowing into the same VMR branch and target directory

These misconfigurations can lead to race conditions, merge conflicts,
and unexpected behavior in the dependency flow system.

## Solution

### Comprehensive Validation
Added validation with a shared service architecture:

- **`ICodeflowSubscriptionValidationService`**: Common interface in
`Maestro.Common`
- **`CodeflowSubscriptionValidationService`**: Single implementation
containing all validation logic
- **Server-side validation**: SubscriptionsController validates on
`Create()` and `UpdateSubscription()`
- **Client-side validation**: DARC CLI validates in
`AddSubscriptionOperation` and `UpdateSubscriptionOperation`
- **Shared base class**: `SubscriptionOperationBase` eliminates
duplication between Add/Update operations

### Validation Rules

**Backflow subscriptions** (VMR → repository, `sourceDirectory` set):
- Only one backflow subscription allowed per target repository + target
branch combination

**Forward flow subscriptions** (repository → VMR, `targetDirectory`
set):
- Only one forward flow subscription allowed per VMR repository + VMR
branch + target directory combination

### API Improvement

Replaced the specific `GetCodeflowSubscriptionsAsync` method with a more
generic `GetSubscriptionsAsync` that accepts additional optional
parameters:

```csharp
Task<IEnumerable<Subscription>> GetSubscriptionsAsync(
    string sourceRepo = null,
    string targetRepo = null,
    int? channelId = null,
    bool? sourceEnabled = null,        // New
    string sourceDirectory = null,     // New
    string targetDirectory = null);    // New
```

This provides a cleaner, more flexible API that supports both general
subscription filtering and specific codeflow validation needs without
code duplication.

## Error Messages

Clear, actionable error messages help users understand and resolve
conflicts:

```
A backflow subscription 'abc123' already exists for the same target repository and branch. 
Only one backflow subscription is allowed per target repository and branch combination.
```

## Benefits

- **Maintainable**: Validation logic exists in one place
- **Consistent**: Same validation behavior across all entry points
- **Clean API**: Generic subscription querying without method
duplication
- **No breaking changes**: Existing functionality remains unaffected

Fixes dotnet#5204.

<!-- START COPILOT CODING AGENT TIPS -->
---

✨ Let Copilot coding agent [set things up for
you](https://github.com/dotnet/arcade-services/issues/new?title=✨+Set+up+Copilot+instructions&body=Configure%20instructions%20for%20this%20repository%20as%20documented%20in%20%5BBest%20practices%20for%20Copilot%20coding%20agent%20in%20your%20repository%5D%28https://gh.io/copilot-coding-agent-tips%29%2E%0A%0A%3COnboard%20this%20repo%3E&assignees=copilot)
— coding agent works faster and does higher quality work when set up for
your repo.

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: premun <7013027+premun@users.noreply.github.com>
Co-authored-by: dkurepa <91743470+dkurepa@users.noreply.github.com>