Improve templates fetching logic and filtering

[HellAmbro]

This PR optimizes template fetching by retrieving templates directly for a specific tag instead of fetching all releases and filtering afterward.
Additionally, it streamlines the iteration over assets using a prebuilt asset map for faster lookups.

[codspeed-hq]

CodSpeed Performance Report

Merging #6068 will not alter performance

_{Comparing HellAmbro:improve_templates (1ef3759) with main (5b3aa27)}

Summary

✅ 8 untouched

[greptile-apps]

Greptile Summary

Optimized template fetching by directly querying GitHub API for specific release tag (/tags/v{tag}) instead of fetching all releases and iterating. Improved asset lookup performance by building an asset_map dictionary upfront for O(1) lookups instead of repeated linear searches through assets. Made code more defensive by using .get("templates", []) to handle missing keys gracefully.

Confidence Score: 5/5

• This PR is safe to merge with no risk
• Pure optimization with no behavioral changes - reduces API calls from fetching all releases to fetching one specific release, improves asset lookup from O(n*m) to O(m) via prebuilt map, adds defensive error handling, and maintains functional equivalence with original code
• No files require special attention

Important Files Changed

Filename	Overview
reflex/utils/templates.py	Optimized template fetching to query specific release by tag instead of fetching all releases, improved asset lookup performance with prebuilt map

Sequence Diagram

sequenceDiagram
    participant Client as fetch_app_templates
    participant API as GitHub API
    participant Assets as Release Assets

    Note over Client,API: OLD: Fetch all releases
    Client->>API: GET /repos/reflex-dev/templates/releases
    API-->>Client: All releases [...]
    Client->>Client: Iterate releases to find tag match
    
    Note over Client,Assets: OLD: Linear search for each template
    loop For each template
        Client->>Assets: Search assets array for template.zip
        Assets-->>Client: Return URL or None
    end

    Note over Client,API: NEW: Direct tag query (optimized)
    Client->>API: GET /releases/tags/v{tag}
    alt Release exists
        API-->>Client: Specific release data
        Client->>Client: Build asset_map dictionary (O(1) lookups)
        Client->>API: GET templates.json from asset_map
        API-->>Client: templates.json content
        loop For each template
            Client->>Client: Lookup code_url in asset_map (O(1))
        end
    else Release not found
        API-->>Client: 404 Not Found
        Client->>Client: Return empty dict
    end

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[greptile-apps]

Additional Comments (1)

1. reflex/utils/templates.py, line 284-287 (link)

   logic: Cannot assign to code_url field because Template is a frozen dataclass (line 15). This will raise dataclasses.FrozenInstanceError at runtime.

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[greptile-apps]

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