Fix: Environment variables can be duplicated on run (#1218)

## Type of Change
- [x] Bug fix
- [ ] New feature  
- [ ] Breaking change
- [ ] Documentation update

## Motivation and Context
As reported in [1212](#1212),
environment variables defined in a Dockerfile (ENV) were not being
overridden when passed via -e at runtime, resulting in duplicate entries
in the container's environment.

**Root cause:** `Parser.allEnv()` simply merged image, env-file, and
user-provided environment variables without deduplication. Since
`getenv()` returns the first match, the image default took precedence
over the user override.

**Fix:** `allEnv()` now deduplicates by key, with later sources
overriding earlier ones

## Testing
- [x] Tested locally
- [x] Added/updated tests
- [ ] Added/updated docs

Author: simone-panico

Sources/Services/ContainerAPIService/Client/Parser.swift

@@ -98,14 +98,20 @@ public struct Parser {
     }
 
     public static func allEnv(imageEnvs: [String], envFiles: [String], envs: [String]) throws -> [String] {
-        var output: [String] = []
-        output.append(contentsOf: Parser.env(envList: imageEnvs))
+        var combined: [String] = []
+        combined.append(contentsOf: Parser.env(envList: imageEnvs))
         for envFile in envFiles {
             let content = try Parser.envFile(path: envFile)
-            output.append(contentsOf: content)
+            combined.append(contentsOf: content)
         }
-        output.append(contentsOf: Parser.env(envList: envs))
-        return output
+        combined.append(contentsOf: Parser.env(envList: envs))
+
+        let deduped = combined.reduce(into: [String: String]()) { map, entry in
+            let key = String(entry.split(separator: "=", maxSplits: 1).first ?? Substring(entry))
+            map[key] = entry
+        }
+
+        return deduped.map { $0.value }
     }
 
     public static func envFile(path: String) throws -> [String] {

Tests/ContainerAPIClientTests/ParserTest.swift

@@ -553,6 +553,42 @@ struct ParserTest {
         #expect(result == ["EMPTY="])
     }
 
+    @Test
+    func testAllEnvUserOverridesImage() throws {
+        let result = try Parser.allEnv(
+            imageEnvs: ["FOO=fromimage", "BAR=kept"],
+            envFiles: [],
+            envs: ["FOO=fromuser"]
+        )
+        #expect(Set(result) == Set(["FOO=fromuser", "BAR=kept"]))
+    }
+
+    @Test
+    func testAllEnvFileOverridesImage() throws {
+        let tmpFile = try tmpFileWithContent("FOO=fromfile\n")
+        defer { try? FileManager.default.removeItem(at: tmpFile) }
+
+        let result = try Parser.allEnv(
+            imageEnvs: ["FOO=fromimage", "BAR=kept"],
+            envFiles: [tmpFile.path],
+            envs: []
+        )
+        #expect(Set(result) == Set(["FOO=fromfile", "BAR=kept"]))
+    }
+
+    @Test
+    func testAllEnvUserOverridesFileOverridesImage() throws {
+        let tmpFile = try tmpFileWithContent("FOO=fromfile\nBAZ=fromfile\n")
+        defer { try? FileManager.default.removeItem(at: tmpFile) }
+
+        let result = try Parser.allEnv(
+            imageEnvs: ["FOO=fromimage", "BAR=fromimage"],
+            envFiles: [tmpFile.path],
+            envs: ["FOO=fromuser"]
+        )
+        #expect(Set(result) == Set(["FOO=fromuser", "BAR=fromimage", "BAZ=fromfile"]))
+    }
+
     private func tmpFileWithContent(_ content: String) throws -> URL {
         let tempDir = FileManager.default.temporaryDirectory
         let tempFile = tempDir.appendingPathComponent("envfile-test-\(UUID().uuidString)")