bug: .taskrc parser silently truncates values containing '=' characters causing silent authentication failures

### Describe your issue

The `.taskrc` parser in `lib/app/utils/taskserver/parse_taskrc.dart`
uses `line.split('=')` to parse key-value pairs. This causes silent
data truncation for any parameter whose value contains one or more `=`
characters.

This is a critical bug because base64-encoded certificates and other
taskd parameter values routinely contain `=` padding characters. When
these values are truncated, authentication silently fails with
absolutely no error shown to the user — making it nearly impossible
to diagnose.

Root Cause:
File: lib/app/utils/taskserver/parse_taskrc.dart
Line: 7-8

The parser does:

.map((line) => line.split('='))

and then blindly extracts pair[0] and pair[1]. When a value contains
`=` (e.g. base64 padding), split('=') produces 3+ parts — everything
from pair[2] onwards is permanently dropped.

Example:
Input: taskd.certificate=abc123==
split result: ['taskd.certificate', 'abc123', '', '']
Stored: 'abc123' ← trailing == silently lost

### Steps to reproduce

1. Create a .taskrc file containing any parameter whose value includes
one or more '=' characters, for example:

taskd.certificate=LS0tLS1CRUdJTiBDRVJUSUZJQ0FURS0tLS0t==

2. Import this .taskrc into the app during TaskServer configuration setup

3. Tap "Taskrc file is verified" to inspect the parsed configuration

4. Observe: everything after the second '=' in the value is silently
dropped from the stored configuration

### What was the expected result?

The parser should split only on the first occurrence of '=' and
preserve the entire remainder of the line as the value.

The correct fix is to replace line.split('=') with a first-occurrence
split:

final index = line.indexOf('=');
if (index == -1) return; // skip malformed lines
final key = line.substring(0, index).trim();
final value = line.substring(index + 1).trim();

This correctly handles all values containing '=' characters including
base64-encoded certificates, credentials, and taskd.trust parameters.

Impact:
- Any user with base64-encoded certificates in their .taskrc is
silently affected
- Directly contributes to the root cause of issue #428 (taskd.trust
being ignored) since cert fields with '=' padding are dropped before
reaching the SSL handshake
- Authentication silently fails with no error surfaced to the user
- Affects all platforms: Android, Linux, Windows, macOS

### Put here any screenshots or videos (optional)

N/A — this is a code-level parser bug reproducible by reading
lib/app/utils/taskserver/parse_taskrc.dart lines 7-8

### How can we contact you (optional)

Available on CCExtractor Zulip: [Varad Raj Agrawal](https://ccextractor.zulipchat.com/#user/1034985)

### Would you like to work on this issue?

Yes

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